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How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment
From large-scale agriculture and farming to concentrated fishing discards, garbage dumps, game carcasses and bird feeders, human action has been increasingly affecting natural systems and animal species through the deliberate and unintentional provisioning of food resources. Anthropogenic food sourc...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2022
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| _version_ | 1867614323305611264 |
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| access_status_str | Open Access |
| author | Jain, Varalika |
| author2 | Sumasgutner, Petra |
| author_browse | Jain, Varalika Sumasgutner, Petra |
| author_facet | Sumasgutner, Petra Jain, Varalika |
| author_sort | Jain, Varalika |
| collection | Thesis |
| description | From large-scale agriculture and farming to concentrated fishing discards, garbage dumps, game carcasses and bird feeders, human action has been increasingly affecting natural systems and animal species through the deliberate and unintentional provisioning of food resources. Anthropogenic food sources (AFSs) are often more spatially concentrated, easily accessible, abundant and stable than natural food sources. The common raven, Corvus corax, is a behaviourally flexible and ecologically adaptable species that has managed to thrive in human transformed landscapes by exploiting these anthropogenic sources of food. The aim of this research was to investigate how raven individuals vary in their use of different AFSs through space and time. I used data from a long-term GPS tracking initiative in the Upper Austrian Alps to investigate (1) the space-use of non-breeding raven individuals across this landscape to answer the questions: (2) what types of AFSs are most extensively used by ravens in this landscape, and what factors predict individual variation in AFS use (i.e., apparent reliance on and access to resources), specifically (3a) the number of AFSs visited and (3b) the probability of being at AFSs at any given point in time. Movement patterns can reveal information on the foraging decisions made by individuals, including how they use different AFSs. Non-breeding raven individuals exhibited great variation in how they moved around and used the landscape. The number of AFSs visited, but not the probability of being at an AFS (at any given point in time), varied among individuals with different ranging behaviour and of different age class (i.e., juvenile and adults) and origin (i.e., captive-bred-released and wild-caught), suggesting that experience affects AFS-use. Non-breeders differed in their use of AFSs by season, visiting the highest number of AFSs but having the lowest probability being present at an AFS in winter, potentially indicative of high foraging competition under stressful environmental conditions. They were also found to extensively exploit resources in spring, both visiting high numbers of AFSs and having a high probability of being present at an AFS, perhaps due to decreased competition (e.g., from breeders) and increases in food availability. The category (i.e., wildpark, refuse site, hut) of AFSs also influenced the probability of an individual being present at the site, likely because of differences in resource quality, quantity and replenishing rate. A very few foraging sites were highly popular, while over half attracted less than 5 individuals throughout the study. By exploiting AFSs, raven population numbers have increased across their range, raising conservation concerns (i.e., predation on threatened species and human-wildlife conflict). With a better understanding of the patterns of AFS-use and the factors influencing these patterns, I suggest that strategies to manage ravens in this semi-transformed, alpine environment should focus on controlling the supply of food at AFSs at a regional scale. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/35786 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:50:13.089Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/35786 How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment Jain, Varalika Sumasgutner, Petra Cunningham, Susan Bugnyar, Thomas Loretto, Matthias Conservation Biology Non-breeder food subsidy space-use resource-use hyperpredation From large-scale agriculture and farming to concentrated fishing discards, garbage dumps, game carcasses and bird feeders, human action has been increasingly affecting natural systems and animal species through the deliberate and unintentional provisioning of food resources. Anthropogenic food sources (AFSs) are often more spatially concentrated, easily accessible, abundant and stable than natural food sources. The common raven, Corvus corax, is a behaviourally flexible and ecologically adaptable species that has managed to thrive in human transformed landscapes by exploiting these anthropogenic sources of food. The aim of this research was to investigate how raven individuals vary in their use of different AFSs through space and time. I used data from a long-term GPS tracking initiative in the Upper Austrian Alps to investigate (1) the space-use of non-breeding raven individuals across this landscape to answer the questions: (2) what types of AFSs are most extensively used by ravens in this landscape, and what factors predict individual variation in AFS use (i.e., apparent reliance on and access to resources), specifically (3a) the number of AFSs visited and (3b) the probability of being at AFSs at any given point in time. Movement patterns can reveal information on the foraging decisions made by individuals, including how they use different AFSs. Non-breeding raven individuals exhibited great variation in how they moved around and used the landscape. The number of AFSs visited, but not the probability of being at an AFS (at any given point in time), varied among individuals with different ranging behaviour and of different age class (i.e., juvenile and adults) and origin (i.e., captive-bred-released and wild-caught), suggesting that experience affects AFS-use. Non-breeders differed in their use of AFSs by season, visiting the highest number of AFSs but having the lowest probability being present at an AFS in winter, potentially indicative of high foraging competition under stressful environmental conditions. They were also found to extensively exploit resources in spring, both visiting high numbers of AFSs and having a high probability of being present at an AFS, perhaps due to decreased competition (e.g., from breeders) and increases in food availability. The category (i.e., wildpark, refuse site, hut) of AFSs also influenced the probability of an individual being present at the site, likely because of differences in resource quality, quantity and replenishing rate. A very few foraging sites were highly popular, while over half attracted less than 5 individuals throughout the study. By exploiting AFSs, raven population numbers have increased across their range, raising conservation concerns (i.e., predation on threatened species and human-wildlife conflict). With a better understanding of the patterns of AFS-use and the factors influencing these patterns, I suggest that strategies to manage ravens in this semi-transformed, alpine environment should focus on controlling the supply of food at AFSs at a regional scale. 2022-02-21T09:50:58Z 2022-02-21T09:50:58Z 2021 2022-02-16T09:10:42Z Master Thesis Masters MSc http://hdl.handle.net/11427/35786 eng application/pdf Department of Biological Sciences Faculty of Science |
| spellingShingle | Conservation Biology Non-breeder food subsidy space-use resource-use hyperpredation Jain, Varalika How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| thesis_degree_str | Master's |
| title | How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| title_full | How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| title_fullStr | How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| title_full_unstemmed | How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| title_short | How common ravens (Corvus corax) exploit anthropogenic food sources through time and space in a semi-transformed, alpine environment |
| title_sort | how common ravens corvus corax exploit anthropogenic food sources through time and space in a semi transformed alpine environment |
| topic | Conservation Biology Non-breeder food subsidy space-use resource-use hyperpredation |
| url | http://hdl.handle.net/11427/35786 |
| work_keys_str_mv | AT jainvaralika howcommonravenscorvuscoraxexploitanthropogenicfoodsourcesthroughtimeandspaceinasemitransformedalpineenvironment |