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Jain V, Bugnyar T, Cunningham SJ, Gallego-Abenza M, Loretto MC, Sumasgutner P. The spatial and temporal exploitation of anthropogenic food sources by common ravens (Corvus corax) in the Alps. MOVEMENT ECOLOGY 2022; 10:35. [PMID: 36008849 PMCID: PMC9414151 DOI: 10.1186/s40462-022-00335-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 08/05/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Anthropogenic food sources (AFSs) are widespread in human-transformed landscapes and the current scale at which they occur drives ecological change at the individual, population, and community levels. AFSs are exploited extensively by common ravens, Corvus corax. Understanding how raven populations use AFSs can provide insight into their ecological responses to AFSs. METHODS We equipped 81 ravens in the Austrian Alps with GPS-transmitters over a period of 2.75 years. Using these tracking data, we investigated how cohort differences (i.e., age, sex, and origin) and seasonal changes influence raven movement patterns (i.e., occurrence distribution and maximum daily displacement) and AFS-use (i.e., number of AFSs visited and probability of being present at any AFS) at 45 extensively exploited sites. RESULTS We found that proxies for experience and dominance, inferred by age (i.e., juvenile versus adult) and origin (i.e., wild-caught versus captive-bred-released) cohorts, influenced movement patterns and the number of AFSs visited. However, all individuals were equally likely to be present at AFSs, highlighting the importance of AFSs for non-breeders in the study population. Seasonal changes in environmental conditions that affect energetic demands, the availability of natural and anthropogenic food, and foraging competition, influenced individuals' occurrence distributions and AFS-use. We found that under harsher conditions in autumn and winter, individuals ranged wider and depended on AFSs to a larger degree. However, contrary to expectation, they were less likely to be present at AFSs in these seasons compared to spring and summer, suggesting a trade-off between time spent moving and exploiting resources. We attribute the small ranging movements exhibited by non-breeders in spring and summer to the presence of highly territorial and socially dominant breeders. As breeders mostly stay and forage within their territories during these seasons, competition at AFSs decrease, thereby increasing the likelihood of individuals being present at any AFS. CONCLUSIONS We emphasize that movement and AFS-use differ according to cohort differences and the seasonality of the environment. Our results highlight that predictable AFSs affect foraging strategies among non-breeding ravens. The extent of AFS-exploitation among non-breeding ravens in our study emphasize the potential of AFSs in shaping raven movement and resource-use.
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Affiliation(s)
- Varalika Jain
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Private Bax X3, Rondebosch, Cape Town, 7701, South Africa.
- Core Facility for Behaviour and Cognition, Konrad Lorenz Research Centre, University of Vienna, Fischerau 13, 4645, Grünau im Almtal, Austria.
| | - Thomas Bugnyar
- Core Facility for Behaviour and Cognition, Konrad Lorenz Research Centre, University of Vienna, Fischerau 13, 4645, Grünau im Almtal, Austria
- Department of Behavioural and Cognitive Biology, University of Vienna, Djerasi Platz 1, 1030, Vienna, Austria
| | - Susan J Cunningham
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Private Bax X3, Rondebosch, Cape Town, 7701, South Africa
| | - Mario Gallego-Abenza
- Core Facility for Behaviour and Cognition, Konrad Lorenz Research Centre, University of Vienna, Fischerau 13, 4645, Grünau im Almtal, Austria
- Department of Behavioural and Cognitive Biology, University of Vienna, Djerasi Platz 1, 1030, Vienna, Austria
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | - Matthias-Claudio Loretto
- Ecosystem Dynamics and Forest Management Group, TUM School of Life Sciences, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, 85354, Freising, Germany
- Berchtesgaden National Park, Doktorberg 6, 83471, Berchtesgaden, Germany
| | - Petra Sumasgutner
- Core Facility for Behaviour and Cognition, Konrad Lorenz Research Centre, University of Vienna, Fischerau 13, 4645, Grünau im Almtal, Austria
- Department of Behavioural and Cognitive Biology, University of Vienna, Djerasi Platz 1, 1030, Vienna, Austria
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Vultures as an overlooked model in cognitive ecology. Anim Cogn 2021; 25:495-507. [PMID: 34817739 DOI: 10.1007/s10071-021-01585-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 10/19/2022]
Abstract
Despite important recent advances in cognitive ecology, our current understanding of avian cognition still largely rests on research conducted on a few model taxa. Vultures are an ecologically distinctive group of species by being the only obligate carrion consumers across terrestrial vertebrates. Their unique scavenging lifestyle suggests they have been subject to particular selective pressures to locate scarce, unpredictable, ephemeral, and nutritionally challenging food. However, substantial variation exists among species in diet, foraging techniques and social structure of populations. Here, we provide an overview of the current knowledge on vulture cognition through a comprehensive literature review and a compilation of our own observations. We find evidence for a variety of innovative foraging behaviors, scrounging tactics, collective problem-solving abilities and tool-use, skills that are considered indicative of enhanced cognition and that bear clear connections with the eco-social lifestyles of species. However, we also find that the cognitive basis of these skills remain insufficiently studied, and identify new research areas that require further attention in the future. Despite these knowledge gaps and the challenges of working with such large animals, we conclude that vultures may provide fresh insight into our knowledge of the ecology and evolution of cognition.
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Gallego-Abenza M, Blum CR, Bugnyar T. Who is crying wolf? Seasonal effect on antipredator response to age-specific alarm calls in common ravens, Corvus corax. Learn Behav 2021; 49:159-167. [PMID: 33420703 PMCID: PMC7979661 DOI: 10.3758/s13420-020-00455-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2020] [Indexed: 11/12/2022]
Abstract
Communication about threats including those posed by the presence of predators occurs mainly through acoustic signals called alarm calls. The comprehension of these calls by receivers and their rapid antipredator response are crucial in terms of survival. However, to avoid overreaction, individuals should evaluate whether or not an antipredator response is needed by paying attention to who is calling. For instance, we could expect adults to be more experienced with predator encounters than juveniles and thus elicit stronger antipredator responses in others when alarming. Similarly, we could expect a stronger response to alarm calls when more than one individual is calling. To test these assumptions, we applied a playback experiment to wild ravens, in which we manipulated the age class (adult or juvenile) and the number (one or two) of the callers. Our results revealed a seasonal effect of age class but no effect of number of callers. Specifically, the ravens responded with stronger antipredator behaviour (vigilance posture) towards alarm calls from adults as compared to juveniles in summer and autumn, but not in spring. We discuss alternative interpretations for this unexpected seasonal pattern and argue for more studies on call-based communication in birds to understand what type of information is relevant under which conditions.
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Affiliation(s)
- Mario Gallego-Abenza
- Department of Behavioural and Cognitive Biology, University of Vienna, Vienna, Austria.
- Konrad Lorenz Forschungsstelle, Core Facility for Behaviour and Cognition, University of Vienna, Grünau im Almtal, Austria.
| | - Christian R Blum
- Department of Behavioural and Cognitive Biology, University of Vienna, Vienna, Austria
| | - Thomas Bugnyar
- Department of Behavioural and Cognitive Biology, University of Vienna, Vienna, Austria
- Konrad Lorenz Forschungsstelle, Core Facility for Behaviour and Cognition, University of Vienna, Grünau im Almtal, Austria
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