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Ellis S, Franks DW, Nielsen MLK, Weiss MN, Croft DP. The evolution of menopause in toothed whales. Nature 2024; 627:579-585. [PMID: 38480878 PMCID: PMC10954554 DOI: 10.1038/s41586-024-07159-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 02/05/2024] [Indexed: 03/20/2024]
Abstract
Understanding how and why menopause has evolved is a long-standing challenge across disciplines. Females can typically maximize their reproductive success by reproducing for the whole of their adult life. In humans, however, women cease reproduction several decades before the end of their natural lifespan1,2. Although progress has been made in understanding the adaptive value of menopause in humans3,4, the generality of these findings remains unclear. Toothed whales are the only mammal taxon in which menopause has evolved several times5, providing a unique opportunity to test the theories of how and why menopause evolves in a comparative context. Here, we assemble and analyse a comparative database to test competing evolutionary hypotheses. We find that menopause evolved in toothed whales by females extending their lifespan without increasing their reproductive lifespan, as predicted by the 'live-long' hypotheses. We further show that menopause results in females increasing their opportunity for intergenerational help by increasing their lifespan overlap with their grandoffspring and offspring without increasing their reproductive overlap with their daughters. Our results provide an informative comparison for the evolution of human life history and demonstrate that the same pathway that led to menopause in humans can also explain the evolution of menopause in toothed whales.
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Affiliation(s)
- Samuel Ellis
- Centre for Research in Animal Behaviour, Department of Psychology, University of Exeter, Exeter, UK.
| | | | | | - Michael N Weiss
- Centre for Research in Animal Behaviour, Department of Psychology, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbor, WA, USA
| | - Darren P Croft
- Centre for Research in Animal Behaviour, Department of Psychology, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbor, WA, USA
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2
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Hart JDA, Weiss MN, Franks DW, Brent LJN. BISoN: A Bayesian Framework for Inference of Social Networks. Methods Ecol Evol 2023; 14:2411-2420. [PMID: 38463700 PMCID: PMC10923527 DOI: 10.1111/2041-210x.14171] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 02/02/2023] [Indexed: 03/12/2024]
Abstract
Animal social networks are often constructed from point estimates of edge weights. In many contexts, edge weights are inferred from observational data, and the uncertainty around estimates can be affected by various factors. Though this has been acknowledged in previous work, methods that explicitly quantify uncertainty in edge weights have not yet been widely adopted, and remain undeveloped for many common types of data. Furthermore, existing methods are unable to cope with some of the complexities often found in observational data, and do not propagate uncertainty in edge weights to subsequent statistical analyses.We introduce a unified Bayesian framework for modelling social networks based on observational data. This framework, which we call BISoN, can accommodate many common types of observational social data, can capture confounds and model effects at the level of observations, and is fully compatible with popular methods used in social network analysis.We show how the framework can be applied to common types of data and how various types of downstream statistical analyses can be performed, including non-random association tests and regressions on network properties.Our framework opens up the opportunity to test new types of hypotheses, make full use of observational datasets, and increase the reliability of scientific inferences. We have made both an R package and example R scripts available to enable adoption of the framework.
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Affiliation(s)
- Jordan D A Hart
- University of Exeter - Department of Psychology, Washington Singer Building Perry Road Exeter, Exeter, Devon EX4 4QJ, United Kingdom of Great Britain and Northern Ireland
| | - Michael N Weiss
- Centre for Research in Animal Behaviour, Exeter, United Kingdom of Great Britain and Northern Ireland, Center for Whale Research, Friday Harbor, United Kingdom of Great Britain and Northern Ireland
| | - Daniel W Franks
- University of York - Biology, The University of York Heslington, York YO105DD, United Kingdom of Great Britain and Northern Ireland
| | - Lauren J N Brent
- University of Exeter - Center for Research in Animal Behaviour, Exeter, United Kingdom of Great Britain and Northern Ireland
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3
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Grimes C, Brent LJN, Ellis S, Weiss MN, Franks DW, Ellifrit DK, Croft DP. Postreproductive female killer whales reduce socially inflicted injuries in their male offspring. Curr Biol 2023; 33:3250-3256.e4. [PMID: 37478863 DOI: 10.1016/j.cub.2023.06.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/13/2023] [Accepted: 06/13/2023] [Indexed: 07/23/2023]
Abstract
Understanding the evolution of menopause presents a long-standing scientific challenge1,2,3-why should females cease ovulation prior to the end of their natural lifespan? In human societies, intergenerational resource transfers, for example, food sharing and caregiving, are thought to have played a key role in the evolution of menopause, providing a pathway by which postreproductive females can boost the fitness of their kin.4,5,6 To date however, other late-life contributions that postreproductive females may provide their kin have not been well studied. Here, we test the hypothesis that postreproductive female resident killer whales (Orcinus orca) provide social support to their offspring by reducing the socially inflicted injuries they experience. We found that socially inflicted injuries, as quantified by tooth rake marks, are lower for male offspring in the presence of their postreproductive mother. In contrast, we find no evidence that postreproductive mothers reduce rake marking in their daughters. Similarly, we find no evidence that either reproductive mothers or grandmothers (reproductive or postreproductive) reduce socially inflicted injuries in their offspring and grandoffspring, respectively. Moreover, we find that postreproductive females have no effect on reducing the rake marks for whales in their social unit who are not their offspring. Taken together, our results highlight that directing late-life support may be a key pathway by which postreproductive females transfer social benefits to their male offspring.
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Affiliation(s)
- Charli Grimes
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG Exeter, UK.
| | - Lauren J N Brent
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG Exeter, UK
| | - Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG Exeter, UK
| | - Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG Exeter, UK; Center for Whale Research, Friday Harbor, WA 98250, USA
| | - Daniel W Franks
- Department of Biology, University of York, YO10 5DD York, UK
| | | | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG Exeter, UK.
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4
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Gaydos JK, St Leger J, Raverty S, Nollens H, Haulena M, Ward EJ, Emmons CK, Hanson MB, Balcomb K, Ellifrit D, Weiss MN, Giles D. Epidemiology of skin changes in endangered Southern Resident killer whales (Orcinus orca). PLoS One 2023; 18:e0286551. [PMID: 37379317 DOI: 10.1371/journal.pone.0286551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/18/2023] [Indexed: 06/30/2023] Open
Abstract
Photographic identification catalogs of individual killer whales (Orcinus orca) over time provide a tool for remote health assessment. We retrospectively examined digital photographs of Southern Resident killer whales in the Salish Sea to characterize skin changes and to determine if they could be an indicator of individual, pod, or population health. Using photographs collected from 2004 through 2016 from 18,697 individual whale sightings, we identified six lesions (cephalopod, erosions, gray patches, gray targets, orange on gray, and pinpoint black discoloration). Of 141 whales that were alive at some point during the study, 99% had photographic evidence of skin lesions. Using a multivariate model including age, sex, pod, and matriline across time, the point prevalence of the two most prevalent lesions, gray patches and gray targets, varied between pods and between years and showed small differences between stage classes. Despite minor differences, we document a strong increase in point prevalence of both lesion types in all three pods from 2004 through 2016. The health significance of this is not clear, but the possible relationship between these lesions and decreasing body condition and immunocompetence in an endangered, non-recovering population is a concern. Understanding the etiology and pathogenesis of these lesions is important to better understand the health significance of these skin changes that are increasing in prevalence.
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Affiliation(s)
- Joseph K Gaydos
- The SeaDoc Society, Karen C. Drayer Wildlife Health Center - Orcas Island Office, UC Davis School of Veterinary Medicine, Eastsound, Washington, United States of America
| | - Judy St Leger
- SeaWorld Parks and Entertainment, San Diego, California, United States of America
| | - Stephen Raverty
- Animal Health Center, Ministry of Agriculture, Abbotsford, British Columbia, Canada
| | - Hendrik Nollens
- SeaWorld Parks and Entertainment, San Diego, California, United States of America
| | | | - Eric J Ward
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - Candice K Emmons
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - M Bradley Hanson
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America
| | - Ken Balcomb
- Center for Whale Research, Friday Harbor, Washington, United States of America
| | - Dave Ellifrit
- Center for Whale Research, Friday Harbor, Washington, United States of America
| | - Michael N Weiss
- Center for Whale Research, Friday Harbor, Washington, United States of America
| | - Deborah Giles
- Center for Whale Research, Friday Harbor, Washington, United States of America
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Abstract
Michael Weiss and Darren Croft introduce Orcas (Orcinus orca) also known as killer whales.
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Affiliation(s)
- Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK; Center for Whale Research, Friday Harbor, WA, USA
| | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK.
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Nielsen MLK, Ellis S, Weiss MN, Towers JR, Doniol-Valcroze T, Franks DW, Cant MA, Ellis GM, Ford JKB, Malleson M, Sutton GJ, Shaw TJH, Balcomb KC, Ellifrit DK, Croft DP. Temporal dynamics of mother-offspring relationships in Bigg's killer whales: opportunities for kin-directed help by post-reproductive females. Proc Biol Sci 2023; 290:20230139. [PMID: 37282537 DOI: 10.1098/rspb.2023.0139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023] Open
Abstract
Age-related changes in the patterns of local relatedness (kinship dynamics) can be a significant selective force shaping the evolution of life history and social behaviour. In humans and some species of toothed whales, average female relatedness increases with age, which can select for a prolonged post-reproductive lifespan in older females due to both costs of reproductive conflict and benefits of late-life helping of kin. Killer whales (Orcinus orca) provide a valuable system for exploring social dynamics related to such costs and benefits in a mammal with an extended post-reproductive female lifespan. We use more than 40 years of demographic and association data on the mammal-eating Bigg's killer whale to quantify how mother-offspring social relationships change with offspring age and identify opportunities for late-life helping and the potential for an intergenerational reproductive conflict. Our results suggest a high degree of male philopatry and female-biased budding dispersal in Bigg's killer whales, with some variability in the dispersal rate for both sexes. These patterns of dispersal provide opportunities for late-life helping particularly between mothers and their adult sons, while partly mitigating the costs of mother-daughter reproductive conflict. Our results provide an important step towards understanding why and how menopause has evolved in Bigg's killer whales.
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Affiliation(s)
| | - Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbor, WA, USA
| | - Jared R Towers
- Bay Cetology, Alert Bay, British Columbia, Canada
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | | | | | - Michael A Cant
- Faculty of Environment, Science and Economy, University of Exeter, Penryn, UK
| | - Graeme M Ellis
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | - John K B Ford
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | - Mark Malleson
- Center for Whale Research, Friday Harbor, WA, USA
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | - Gary J Sutton
- Bay Cetology, Alert Bay, British Columbia, Canada
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | - Tasli J H Shaw
- Bay Cetology, Alert Bay, British Columbia, Canada
- Pacific Biological Station, Fisheries and Oceans Canada, British Columbia, Canada
| | | | | | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
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Weiss MN, Ellis S, Franks DW, Nielsen MLK, Cant MA, Johnstone RA, Ellifrit DK, Balcomb KC, Croft DP. Costly lifetime maternal investment in killer whales. Curr Biol 2023; 33:744-748.e3. [PMID: 36758545 DOI: 10.1016/j.cub.2022.12.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/07/2022] [Accepted: 12/21/2022] [Indexed: 02/11/2023]
Abstract
Parents often sacrifice their own future reproductive success to boost the survival of their offspring, a phenomenon referred to as parental investment. In several social mammals, mothers continue to improve the survival of their offspring well into adulthood;1,2,3,4,5 however, whether this extended care comes at a reproductive costs to mothers, and therefore represents maternal investment, is not well understood. We tested whether lifetime maternal care is a form of parental investment in fish-eating "resident" killer whales. Adult killer whales, particularly males, are known to receive survival benefits from their mothers;3 however, whether this comes at a cost to mothers' reproductive success is not known. Using multiple decades of complete census data from the "southern resident" population, we found a strong negative correlation between females' number of surviving weaned sons and their annual probability of producing a viable calf. This negative effect did not attenuate as sons grew older, and the cost of sons could not be explained by long-term costs of lactation or group composition effects, supporting the hypothesis that caring for adult sons is reproductively costly. This is the first direct evidence of lifetime maternal investment in an iteroparous animal, revealing a previously unknown life history strategy.
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Affiliation(s)
- Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG, Exeter, UK; Center for Whale Research, Friday Harbor, WA 98250, USA.
| | - Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG, Exeter, UK
| | - Daniel W Franks
- Department of Biology, University of York, YO10 5DD, York, UK; Department of Computer Science, University of York, YO10 5DD, York, UK
| | | | - Michael A Cant
- College of Life and Environmental Sciences, University of Exeter, Penryn, TR10 9FE, UK
| | - Rufus A Johnstone
- Department of Zoology, University of Cambridge, CB2 3EJ, Cambridge, UK
| | | | | | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, EX4 4QG, Exeter, UK
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Ellis S, Johnstone RA, Cant MA, Franks DW, Weiss MN, Alberts SC, Balcomb KC, Benton CH, Brent LJN, Crockford C, Davidian E, Delahay RJ, Ellifrit DK, Höner OP, Meniri M, McDonald RA, Nichols HJ, Thompson FJ, Vigilant L, Wittig RM, Croft DP. Patterns and consequences of age-linked change in local relatedness in animal societies. Nat Ecol Evol 2022; 6:1766-1776. [PMID: 36163259 PMCID: PMC10423498 DOI: 10.1038/s41559-022-01872-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 08/01/2022] [Indexed: 11/09/2022]
Abstract
The ultimate payoff of behaviours depends not only on their direct impact on an individual, but also on the impact on their relatives. Local relatedness-the average relatedness of an individual to their social environment-therefore has profound effects on social and life history evolution. Recent work has begun to show that local relatedness has the potential to change systematically over an individual's lifetime, a process called kinship dynamics. However, it is unclear how general these kinship dynamics are, whether they are predictable in real systems and their effects on behaviour and life history evolution. In this study, we combine modelling with data from real systems to explore the extent and impact of kinship dynamics. We use data from seven group-living mammals with diverse social and mating systems to demonstrate not only that kinship dynamics occur in animal systems, but also that the direction and magnitude of kinship dynamics can be accurately predicted using a simple model. We use a theoretical model to demonstrate that kinship dynamics can profoundly affect lifetime patterns of behaviour and can drive sex differences in helping and harming behaviour across the lifespan in social species. Taken together, this work demonstrates that kinship dynamics are likely to be a fundamental dimension of social evolution, especially when considering age-linked changes and sex differences in behaviour and life history.
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Affiliation(s)
- Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK.
| | | | - Michael A Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | | | - Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbor, WA, USA
| | - Susan C Alberts
- Department of Biology, Duke University, Durham, NC, USA
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
| | | | - Claire H Benton
- National Wildlife Management Centre, Animal and Plant Health Agency, Sand Hutton, York, UK
| | - Lauren J N Brent
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Catherine Crockford
- Institut des Sciences Cognitives, CNRS, Lyon, France
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifique, Abidjan, Côte d'Ivoire
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Eve Davidian
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
- Ngorongoro Hyena Project, Ngorongoro Conservation Area, Arusha, Tanzania
| | - Richard J Delahay
- National Wildlife Management Centre, Animal and Plant Health Agency, Sand Hutton, York, UK
| | | | - Oliver P Höner
- Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
- Ngorongoro Hyena Project, Ngorongoro Conservation Area, Arusha, Tanzania
| | - Magali Meniri
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | - Robbie A McDonald
- Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn, UK
| | | | - Faye J Thompson
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK
| | - Linda Vigilant
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Roman M Wittig
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifique, Abidjan, Côte d'Ivoire
- German Centre for Integrative Biodiversity Research, Leipzig, Germany
| | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
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Hart JDA, Weiss MN, Brent LJN, Franks DW. Common permutation methods in animal social network analysis do not control for non-independence. Behav Ecol Sociobiol 2022; 76:151. [PMID: 36325506 PMCID: PMC9617964 DOI: 10.1007/s00265-022-03254-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/04/2022] [Accepted: 10/10/2022] [Indexed: 11/02/2022]
Abstract
The non-independence of social network data is a cause for concern among behavioural ecologists conducting social network analysis. This has led to the adoption of several permutation-based methods for testing common hypotheses. One of the most common types of analysis is nodal regression, where the relationships between node-level network metrics and nodal covariates are analysed using a permutation technique known as node-label permutations. We show that, contrary to accepted wisdom, node-label permutations do not automatically account for the non-independences assumed to exist in network data, because regression-based permutation tests still assume exchangeability of residuals. The same assumption also applies to the quadratic assignment procedure (QAP), a permutation-based method often used for conducting dyadic regression. We highlight that node-label permutations produce the same p-values as equivalent parametric regression models, but that in the presence of non-independence, parametric regression models can also produce accurate effect size estimates. We also note that QAP only controls for a specific type of non-independence between edges that are connected to the same nodes, and that appropriate parametric regression models are also able to account for this type of non-independence. Based on this, we suggest that standard parametric models could be used in the place of permutation-based methods. Moving away from permutation-based methods could have several benefits, including reducing over-reliance on p-values, generating more reliable effect size estimates, and facilitating the adoption of causal inference methods and alternative types of statistical analysis. Supplementary Information The online version contains supplementary material available at 10.1007/s00265-022-03254-x.
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Affiliation(s)
- Jordan D. A. Hart
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Michael N. Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbour, WA USA
| | - Lauren J. N. Brent
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Daniel W. Franks
- Departments of Biology and Computer Science, University of York, York, UK
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10
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Affiliation(s)
- Jordan D. A. Hart
- Centre for Research in Animal Behaviour University of Exeter Exeter UK
| | - Daniel W. Franks
- Departments of Biology and Computer Science University of York York UK
| | | | - Michael N. Weiss
- Centre for Research in Animal Behaviour University of Exeter Exeter UK
- Center for Whale Research Friday Harbour WA USA
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11
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Croft DP, Weiss MN, Nielsen MLK, Grimes C, Cant MA, Ellis S, Franks DW, Johnstone RA. Kinship dynamics: patterns and consequences of changes in local relatedness. Proc Biol Sci 2021; 288:20211129. [PMID: 34403632 PMCID: PMC8370800 DOI: 10.1098/rspb.2021.1129] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/26/2021] [Indexed: 01/16/2023] Open
Abstract
Mounting evidence suggests that patterns of local relatedness can change over time in predictable ways, a process termed kinship dynamics. Kinship dynamics may occur at the level of the population or social group, where the mean relatedness across all members of the population or group changes over time, or at the level of the individual, where an individual's relatedness to its local group changes with age. Kinship dynamics are likely to have fundamental consequences for the evolution of social behaviour and life history because they alter the inclusive fitness payoffs to actions taken at different points in time. For instance, growing evidence suggests that individual kinship dynamics have shaped the evolution of menopause and age-specific patterns of helping and harming. To date, however, the consequences of kinship dynamics for social evolution have not been widely explored. Here we review the patterns of kinship dynamics that can occur in natural populations and highlight how taking a kinship dynamics approach has yielded new insights into behaviour and life-history evolution. We discuss areas where analysing kinship dynamics could provide new insight into social evolution, and we outline some of the challenges in predicting and quantifying kinship dynamics in natural populations.
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Affiliation(s)
- Darren P. Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Michael N. Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
- Center for Whale Research, Friday Harbour, WA, USA
| | - Mia L. K. Nielsen
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Charli Grimes
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Michael A. Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall, UK
| | - Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Daniel W. Franks
- Department of Biology, University of York, York, UK
- Department of Computer Science, University of York, York, UK
| | - Rufus A. Johnstone
- Behaviour and Evolution Group, Department of Zoology, University of Cambridge, Cambridge, UK
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12
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Nielsen MLK, Ellis S, Towers JR, Doniol‐Valcroze T, Franks DW, Cant MA, Weiss MN, Johnstone RA, Balcomb KC, Ellifrit DK, Croft DP. A long postreproductive life span is a shared trait among genetically distinct killer whale populations. Ecol Evol 2021; 11:9123-9136. [PMID: 34257948 PMCID: PMC8258204 DOI: 10.1002/ece3.7756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/14/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022] Open
Abstract
The extended female postreproductive life span found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged postreproductive life span due to the combined costs of intergenerational reproductive conflict and benefits of late-life helping. Here, we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg's killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg's due to their different social structure. Here, we show that there is a significant postreproductive life span in both ecotypes with >30% of adult female years being lived as postreproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a postreproductive life span. Differences in the magnitude of kinship dynamics however did not influence the timing or duration of the postreproductive life span with females in both ecotypes terminating reproduction before their mid-40s followed by an expected postreproductive period of about 20 years. Our results highlight the important role of kinship dynamics in the evolution of a long postreproductive life span in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among populations.
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Affiliation(s)
| | - Samuel Ellis
- Centre for Research in Animal BehaviourUniversity of ExeterExeterUK
| | - Jared R. Towers
- Pacific Biological StationFisheries and Oceans CanadaVancouverBCCanada
| | | | | | - Michael A. Cant
- College of Life and Environmental SciencesUniversity of ExeterPenrynUK
| | - Michael N. Weiss
- Centre for Research in Animal BehaviourUniversity of ExeterExeterUK
- Center for Whale ResearchFriday HarborWAUSA
| | | | | | | | - Darren P. Croft
- Centre for Research in Animal BehaviourUniversity of ExeterExeterUK
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Weiss MN, Franks DW, Giles DA, Youngstrom S, Wasser SK, Balcomb KC, Ellifrit DK, Domenici P, Cant MA, Ellis S, Nielsen MLK, Grimes C, Croft DP. Age and sex influence social interactions, but not associations, within a killer whale pod. Proc Biol Sci 2021; 288:20210617. [PMID: 34130498 DOI: 10.1098/rspb.2021.0617] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Social structure is a fundamental aspect of animal populations. In order to understand the function and evolution of animal societies, it is important to quantify how individual attributes, such as age and sex, shape social relationships. Detecting these influences in wild populations under natural conditions can be challenging, especially when social interactions are difficult to observe and broad-scale measures of association are used as a proxy. In this study, we use unoccupied aerial systems to observe association, synchronous surfacing, and physical contact within a pod of southern resident killer whales (Orcinus orca). We show that interactions do not occur randomly between associated individuals, and that interaction types are not interchangeable. While age and sex did not detectably influence association network structure, both interaction networks showed significant social homophily by age and sex, and centrality within the contact network was higher among females and young individuals. These results suggest killer whales exhibit interesting parallels in social bond formation and social life histories with primates and other terrestrial social mammals, and demonstrate how important patterns can be missed when using associations as a proxy for interactions in animal social network studies.
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Affiliation(s)
- Michael N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK.,Center for Whale Research, Friday Harbour, WA, USA
| | - Daniel W Franks
- Department of Biology and Department of Computer Science, University of York, York, UK
| | - Deborah A Giles
- Center for Conservation Biology, Department of Biology, University of Washington, Seattle, WA, USA
| | - Sadie Youngstrom
- Center for Conservation Biology, Department of Biology, University of Washington, Seattle, WA, USA
| | - Samuel K Wasser
- Center for Conservation Biology, Department of Biology, University of Washington, Seattle, WA, USA
| | | | | | | | - Michael A Cant
- Centre for Ecology and Conservation, University of Exeter, Penryn, UK
| | - Samuel Ellis
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Mia L K Nielsen
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Charli Grimes
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
| | - Darren P Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK
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14
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Weiss MN, Franks DW, Brent LJN, Ellis S, Silk MJ, Croft DP. Common datastream permutations of animal social network data are not appropriate for hypothesis testing using regression models. Methods Ecol Evol 2020; 12:255-265. [DOI: 10.1111/2041-210x.13508] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Michael N. Weiss
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
- Center for Whale Research Friday Harbor WA USA
| | - Daniel W. Franks
- Department of Biology and Department of Computer Science The University of York York UK
| | - Lauren J. N. Brent
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
| | - Samuel Ellis
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
| | - Matthew J. Silk
- Centre for Ecology and Conservation University of Exeter in Cornwall Penryn UK
| | - Darren P. Croft
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
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15
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Allen CRB, Brent LJN, Motsentwa T, Weiss MN, Croft DP. Importance of old bulls: leaders and followers in collective movements of all-male groups in African savannah elephants (Loxodonta africana). Sci Rep 2020; 10:13996. [PMID: 32883968 PMCID: PMC7471917 DOI: 10.1038/s41598-020-70682-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 06/29/2020] [Indexed: 11/09/2022] Open
Abstract
In long-lived social species, older individuals can provide fitness benefits to their groupmates through the imparting of ecological knowledge. Research in this area has largely focused on females in matrilineal societies where, for example, older female African savannah elephants (Loxodonta africana) are most effective at making decisions crucial to herd survival, and old post-reproductive female resident killer whales (Orcinus orca) lead collective movements in hunting grounds. In contrast, little is known about the role of older males as leaders in long-lived social species. By analysing leadership patterns of all-male African savannah elephant traveling groups along elephant pathways in Makgadikgadi Pans National Park, Botswana, we found that the oldest males were more likely to lead collective movements. Our results challenge the assumption that older male elephants are redundant in the population and raise concerns over the biased removal of old bulls that currently occurs in both legal trophy hunting and illegal poaching. Selective harvesting of older males could have detrimental effects on the wider elephant society through loss of leaders crucial to younger male navigation in unknown, risky environments.
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Affiliation(s)
- Connie R B Allen
- Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QG, UK.
| | - Lauren J N Brent
- Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QG, UK
| | - Thatayaone Motsentwa
- Elephants for Africa, 5 Balfour Road, London, N5 2HB, UK.,Elephants for Africa, Mailbox 148 HAK, Maun, Botswana
| | - Michael N Weiss
- Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QG, UK
| | - Darren P Croft
- Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QG, UK
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16
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Affiliation(s)
- Daniel W. Franks
- Departments of Biology and Computer Science The University of York York UK
| | - Michael N. Weiss
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
| | - Matthew J. Silk
- Environment and Sustainability Institute University of Exeter Penryn UK
| | - Robert J. Y. Perryman
- Department of Biological Sciences Macquarie University Sydney NSW Australia
- Marine Megafauna Foundation Truckee CA USA
| | - Darren P. Croft
- Centre for Research in Animal Behaviour College of Life and Environmental Sciences University of Exeter Exeter UK
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17
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Langley EJG, Horik JO, Whiteside MA, Beardsworth CE, Weiss MN, Madden JR. Early‐life learning ability predicts adult social structure, with potential implications for fitness outcomes in the wild. J Anim Ecol 2020; 89:1340-1349. [DOI: 10.1111/1365-2656.13194] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 01/09/2020] [Indexed: 11/29/2022]
Affiliation(s)
- Ellis J. G. Langley
- Centre for Research in Animal Behaviour, Psychology University of Exeter Exeter UK
| | - Jayden O. Horik
- Centre for Research in Animal Behaviour, Psychology University of Exeter Exeter UK
| | - Mark A. Whiteside
- Centre for Research in Animal Behaviour, Psychology University of Exeter Exeter UK
| | | | - Michael N. Weiss
- Centre for Research in Animal Behaviour, Psychology University of Exeter Exeter UK
| | - Joah R. Madden
- Centre for Research in Animal Behaviour, Psychology University of Exeter Exeter UK
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18
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Ellis S, Franks DW, Nattrass S, Cant MA, Weiss MN, Giles D, Balcomb KC, Croft DP. Mortality risk and social network position in resident killer whales: sex differences and the importance of resource abundance. Proc Biol Sci 2018; 284:rspb.2017.1313. [PMID: 29070720 PMCID: PMC5666093 DOI: 10.1098/rspb.2017.1313] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 09/29/2017] [Indexed: 02/05/2023] Open
Abstract
An individual's ecological environment affects their mortality risk, which in turn has fundamental consequences for life-history evolution. In many species, social relationships are likely to be an important component of an individual's environment, and therefore their mortality risk. Here, we examine the relationship between social position and mortality risk in resident killer whales (Orcinus orca) using over three decades of social and demographic data. We find that the social position of male, but not female, killer whales in their social unit predicts their mortality risk. More socially integrated males have a significantly lower risk of mortality than socially peripheral males, particularly in years of low prey abundance, suggesting that social position mediates access to resources. Male killer whales are larger and require more resources than females, increasing their vulnerability to starvation in years of low salmon abundance. More socially integrated males are likely to have better access to social information and food-sharing opportunities which may enhance their survival in years of low salmon abundance. Our results show that observable variation in the social environment is linked to variation in mortality risk, and highlight how sex differences in social effects on survival may be linked to sex differences in life-history evolution.
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Affiliation(s)
- S Ellis
- Centre for Research in Animal Behaviour, University of Exeter, Exeter EX4 4QG, UK
| | - D W Franks
- Department of Biology, University of York, York YO10 5GE, UK
| | - S Nattrass
- Department of Biology, University of York, York YO10 5GE, UK
| | - M A Cant
- Centre for Ecology and Conservation, University of Exeter in Cornwall, Penryn, Cornwall TR10 9FE, UK
| | - M N Weiss
- Centre for Research in Animal Behaviour, University of Exeter, Exeter EX4 4QG, UK
| | - D Giles
- Center for Whale Research, 355 Smugglers Cove Road, Friday Harbor, WA 98250, USA
| | - K C Balcomb
- Center for Whale Research, 355 Smugglers Cove Road, Friday Harbor, WA 98250, USA
| | - D P Croft
- Centre for Research in Animal Behaviour, University of Exeter, Exeter EX4 4QG, UK
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Weiss MN, Srivastava R. Spectral characteristics of asymmetric directional couplers in graded index channel waveguides analyzed by coupled-mode and normal-mode techniques. Appl Opt 1995; 34:1029-1040. [PMID: 21037630 DOI: 10.1364/ao.34.001029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a detailed analysis of the spectral characteristics of asymmetric directional couplers (ADC's) formed by K(+) -Na(+) ion exchange in BK7 glass and compare the results obtained by the use of normal-mode theory with those obtained by the use of the coupled-mode approach. Maximum power transfer is observed to occur at the wavelength at which the propagation constants of the perturbed component arms are equal. This is attributed to the strong coupling inherent in these devices. Strong coupling and asymmetry are observed to result in unequal confinement of the normal modes, leading to reduce power transfer, even when both arms of the coupler are synchronized. Additionally, significant polarization dependence is observed because of birefringence induced by both the K(+) -Na(+) exchange process and the chosen device structure. Polarization extinction ratios of 11.9 and 26.1 dB are obtained for the arms of the directional couplers. ADC's are observed to operate as bandpass filters, and by adjustment of structural parameters, the peak transmission wavelength can be tuned, with spectral bandwidths of 25-55 nm and coupling lengths of 6-12 mm. Over 90% of the input power in the TE polarization at 1.07 µm can be transferred to the second arm of the coupler, whereas power either in the TM polarization or at wavelengths outside the passband is relatively unaffected. We also show that within the bandpass, where the two arms are phase matched, exact normal-mode analysis yields the same results as the quasi-normal-mode approach, in which the normal modes are expressed in terms of the individual modes.
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Weiss MN, Srivastava R. Determination of ion-exchanged channel waveguide profile parameters by mode-index measurements. Appl Opt 1995; 34:455-458. [PMID: 20963139 DOI: 10.1364/ao.34.000455] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report a method for characterizing ion-exchanged channel waveguides in terms of the diffusion depth, width, and surface-index change from mode-index measurements. The method is then used to study the effect of the diffusion time and the mask width on these parameters in K(+)-Na(+)-exchanged guides in BK7 glass. It is observed that the mask width affects the waveguide dimensions in ways not reported in earlier studies. Our results reveal that the diffusion depth depends on the mask opening and saturates with time to a maximum value for a given mask width. The lateral-diffusion rate and the side diffusion beneath the mask are independent of the mask width, which indicates that the lateral electric field associated with the metallic mask plays an important role in such diffusion. We discuss the implications of this behavior to modeling and fabricating integrated optical devices.
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