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Spiegel O, Michelangeli M, Sinn DL, Payne E, Klein JRV, Kirkpatrick J, Harbusch M, Sih A. Resource manipulation reveals interactive phenotype-dependent foraging in free-ranging lizards. J Anim Ecol 2024. [PMID: 38877691 DOI: 10.1111/1365-2656.14128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 05/07/2024] [Indexed: 06/16/2024]
Abstract
Recent evidence suggests that individuals differ in foraging tactics and this variation is often linked to an individual's behavioural type (BT). Yet, while foraging typically comprises a series of search and handling steps, empirical investigations have rarely considered BT-dependent effects across multiple stages of the foraging process, particularly in natural settings. In our long-term sleepy lizard (Tiliqua rugosa) study system, individuals exhibit behavioural consistency in boldness (measured as an individual's willingness to approach a novel food item in the presence of a threat) and aggressiveness (measured as an individual's response to an 'attack' by a conspecific dummy). These BTs are only weakly correlated and have previously been shown to have interactive effects on lizard space use and movement, suggesting that they could also affect lizard foraging performance, particularly in their search behaviour for food. To investigate how lizards' BTs affect their foraging process in the wild, we supplemented food in 123 patches across a 120-ha study site with three food abundance treatments (high, low and no-food controls). Patches were replenished twice a week over the species' entire spring activity season and feeding behaviours were quantified with camera traps at these patches. We tracked lizards using GPS to determine their home range (HR) size and repeatedly assayed their aggressiveness and boldness in designated assays. We hypothesised that bolder lizards would be more efficient foragers while aggressive ones would be less attentive to the quality of foraging patches. We found an interactive BT effect on overall foraging performance. Individuals that were both bold and aggressive ate the highest number of food items from the foraging array. Further dissection of the foraging process showed that aggressive lizards in general ate the fewest food items in part because they visited foraging patches less regularly, and because they discriminated less between high and low-quality patches when revisiting them. Bolder lizards, in contrast, ate more tomatoes because they visited foraging patches more regularly, and ate a higher proportion of the available tomatoes at patches during visits. Our study demonstrates that BTs can interact to affect different search and handling components of the foraging process, leading to within-population variation in foraging success. Given that individual differences in foraging and movement will influence social and ecological interactions, our results highlight the potential role of BT's in shaping individual fitness strategies and population dynamics.
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Affiliation(s)
- Orr Spiegel
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Marcus Michelangeli
- Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- School of Environment and Science, Griffith University, Nathan, Queensland, Australia
| | - David L Sinn
- Department of Environmental Science and Policy, University of California, Davis, California, USA
| | - Eric Payne
- Department of Environmental Science and Policy, University of California, Davis, California, USA
| | - Janine-Rose V Klein
- Department of Anthropology, University of California, Santa Barbara, California, USA
| | - Jamie Kirkpatrick
- Department of Anthropology, University of California, Santa Barbara, California, USA
| | - Marco Harbusch
- Georg-August-Büsgen-Institut, Universität Göttingen, Göttingen, Germany
| | - Andrew Sih
- Department of Environmental Science and Policy, University of California, Davis, California, USA
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Orlando CG, Banks PB, Latty T, McArthur C. To eat, or not to eat: a phantom decoy affects information-gathering behavior by a free-ranging mammalian herbivore. Behav Ecol 2023; 34:759-768. [PMID: 37744169 PMCID: PMC10516680 DOI: 10.1093/beheco/arad057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 06/09/2023] [Accepted: 06/28/2023] [Indexed: 09/26/2023] Open
Abstract
When foraging, making appropriate food choices is crucial to an animal's fitness. Classic foraging ecology theories assume animals choose food of greatest benefit based on their absolute value across multiple dimensions. Consequently, poorer options are considered irrelevant alternatives that should not influence decision-making among better options. But heuristic studies demonstrate that irrelevant alternatives (termed decoys) can influence the decisions of some animals, indicating they use a relative rather than absolute evaluation system. Our aim was to test whether a decoy influenced the decision-making process-that is, information-gathering and food choice-of a free-ranging mammalian herbivore. We tested swamp wallabies, Wallabia bicolor, comparing their behavior toward, and choice of, two available food options over time in the absence or presence of the decoy. We used a phantom decoy-unavailable option-and ran two trials in different locations and seasons. Binary preferences (decoy absent) for the two available food options differed between trials. Irrespective of this difference, across both trials the presence of the decoy resulted in animals more likely to overtly investigate available food options. But, the decoy only shifted food choice, weakly, in one trial. Our results indicate that the decoy influenced the information-gathering behavior during decision-making, providing the first evidence that decoys can affect decision-making process of free-ranging mammalian herbivores in an ecologically realistic context. It is premature to say these findings confirm the use of relative evaluation systems. Whether the foraging outcome is more strongly affected by other decoys, food dimensions, or ecological contexts, is yet to be determined.
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Affiliation(s)
- Cristian Gabriel Orlando
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building A08, Science Rd., Camperdown, Sydney, NSW 2050, Australia
| | - Peter B Banks
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building A08, Science Rd., Camperdown, Sydney, NSW 2050, Australia
| | - Tanya Latty
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building A08, Science Rd., Camperdown, Sydney, NSW 2050, Australia
| | - Clare McArthur
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building A08, Science Rd., Camperdown, Sydney, NSW 2050, Australia
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Harris H, Wat KKY, Banks PB, Greenville A, McArthur C. Grow up, be persistent, and stay focused: keys for solving foraging problems by free-ranging possums. Behav Ecol 2023; 34:790-803. [PMID: 38046238 PMCID: PMC10690113 DOI: 10.1093/beheco/arad054] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 04/18/2023] [Accepted: 06/12/2023] [Indexed: 12/05/2023] Open
Abstract
Individuals within a species often vary in both their problem-solving approach and ability, affecting their capacity to access novel food resources. Testing problem-solving in free-ranging individuals is crucial for understanding the fundamental ecological implications of problem-solving capacity. To examine the factors affecting problem-solving in free-ranging animals, we presented three food-extraction tasks of increasing difficulty to urban common brushtail possums (Trichosurus vulpecula). We quantified two measures of problem-solving performance: trial outcome (success/failure) and time to solve and tested the influence of a range of potential drivers, including individual traits (personality, body weight, sex, and age), mechanistic behaviors that quantify problem-solving approach (work time, functional behavior time, behavioral diversity, and flexibility), and prior experience with the puzzles. We found that mechanistic behaviors were key drivers of performance. Individuals displaying greater persistence (higher work and functional behavior time) were more likely to solve a food-extraction task on their first attempt. Individuals also solved problems faster if they were more persistent and had lower behavioral flexibility. Personality indirectly affected time to solve one of the three problems by influencing time allocated to functional behaviors. Finally, adults solved the most difficult problem faster than juveniles. Overall, our study provides rare insight into the drivers underlying the problem-solving performance of wild animals. Such insight could be used to improve management strategies and conservation efforts, such as food or bait deployment, tailored to suit the innovative foraging abilities of target individuals in new and changing environments.
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Affiliation(s)
- Hannah Harris
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia
| | - Katie K Y Wat
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia
| | - Peter B Banks
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia
| | - Aaron Greenville
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia
| | - Clare McArthur
- School of Life and Environmental Sciences, The University of Sydney, Heydon-Laurence Building (A08), Sydney, NSW 2006, Australia
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Cockrem JF. Individual variation, personality, and the ability of animals to cope with climate change. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.897314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Sixth Assessment of the Intergovernmental Panel on Climate Change describes negative effects of climate change on animals occurring on a larger scale than previously appreciated. Animal species are increasingly experiencing more frequent and extreme weather in comparison with conditions in which the species evolved. Individual variation in behavioural and physiological responses of animals to stimuli from the environment is ubiquitous across all species. Populations with relatively high levels of individual variation are more likely to be able to survive in a range of environmental conditions and cope with climate change than populations with low levels of variation. Behavioural and physiological responses are linked in animals, and personality can be defined as consistent individual behavioural and physiological responses of animals to changes in their immediate environment. Glucocorticoids (cortisol and corticosterone) are hormones that, in addition to metabolic roles, are released when the neuroendocrine stress system is activated in response to stimuli from the environment perceived to be threatening. The size of a glucocorticoid response of an animal is an indication of the animal’s personality. Animals with reactive personalities have relatively high glucocorticoid responses, are relatively slow and thorough to explore new situations, and are more flexible and able to cope with changing or unpredictable conditions than animals with proactive personalities. Animals with reactive personalities are likely to be better able to cope with environmental changes due to climate change than animals with proactive personalities. A reaction norm shows the relationship between phenotype and environmental conditions, with the slope of a reaction norm for an individual animal a measure of phenotypic plasticity. If reaction norm slopes are not parallel, there is individual variation in plasticity. Populations with relatively high individual variation in plasticity of reaction norms will have more animals that can adjust to a new situation than populations with little variation in plasticity, so are more likely to persist as environments change due to climate change. Future studies of individual variation in plasticity of responses to changing environments will help understanding of how populations of animals may be able to cope with climate change.
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Odewahn R, Wright BR, Czirják GÁ, Higgins DP. Differences in constitutive innate immunity between divergent Australian marsupials. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2022; 132:104399. [PMID: 35307478 DOI: 10.1016/j.dci.2022.104399] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 06/14/2023]
Abstract
Understanding immunity in wildlife populations is important from both One Health and conservation perspectives. The constitutive innate immune system is the first line of defence against pathogens, and comparisons among taxa can test the impact of evolution and life history on immune function. We investigated serum bacterial killing ability (BKA) of five marsupial species that employ varying life history strategies, demonstrated to influence immunity in other vertebrates. The brushtail possum and eastern grey kangaroo had the greatest BKA, while ringtail possums and koalas had the least. These differences were independent of social structure, captivity status and phylogeny, but were associated with diet and body size. Sex and disease status had no effect on BKA in koalas, however potential for differences between wild and captive koalas warrants further investigation. The current study has provided a foundation for future investigations into how adaptive and innate immunity interact in marsupials from an eco-evolutionary perspective.
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Affiliation(s)
- Rebecca Odewahn
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, NSW, Australia
| | - Belinda R Wright
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, NSW, Australia
| | - Gábor Á Czirják
- Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315, Berlin, Germany
| | - Damien P Higgins
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, NSW, Australia.
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