TY - JOUR
T1 - Socially Defined Subpopulations Reveal Demographic Variation in a Giraffe Metapopulation
AU - Bond, Monica L.
AU - König, Barbara
AU - Ozgul, Arpat
AU - Farine, Damien R.
AU - Lee, Derek E.
N1 - Funding Information:
We conducted this research with permission from the Tanzania Commission for Science and Technology, Tanzania National Parks, Tanzania Wildlife Research Institute, Tanzania Wildlife Authority, and African Wildlife Foundation. We thank P. D. McLoughlin and 2 anonymous reviewers for valuable suggestions. Financial support to M. L. Bond was provided by grants from the ‘Forschungskredit UZH’ (Grant Number FK‐16‐080), Parrotia‐Stiftung, and Temperatio‐Stiftung. A. Ozgul was funded by SNF Grant (31003A_182286). D. R. Farine was funded by the Max Planck Society, an Eccellenza Professorship Grant of the Swiss National Science Foundation (Grant Number PCEFP3_187058), the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 850859), and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy—EXC 2117—422037984. Field data collection was funded by Sacramento Zoo, Columbus Zoo, Tulsa Zoo, Tierpark Berlin, Cincinnati Zoo, Como Park Zoo, Zoo Miami, Save the Giraffes, Promotor Foundation, and Claraz Foundation.
Funding Information:
We conducted this research with permission from the Tanzania Commission for Science and Technology, Tanzania National Parks, Tanzania Wildlife Research Institute, Tanzania Wildlife Authority, and African Wildlife Foundation. We thank P. D. McLoughlin and 2 anonymous reviewers for valuable suggestions. Financial support to M. L. Bond was provided by grants from the ?Forschungskredit UZH? (Grant Number FK-16-080), Parrotia-Stiftung, and Temperatio-Stiftung. A. Ozgul was funded by SNF Grant (31003A_182286). D. R. Farine was funded by the Max Planck Society, an Eccellenza Professorship Grant of the Swiss National Science Foundation (Grant Number PCEFP3_187058), the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 850859), and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy?EXC 2117?422037984. Field data collection was funded by Sacramento Zoo, Columbus Zoo, Tulsa Zoo, Tierpark Berlin, Cincinnati Zoo, Como Park Zoo, Zoo Miami, Save the Giraffes, Promotor Foundation, and Claraz Foundation.
Publisher Copyright:
© 2021 The Wildlife Society
PY - 2021/7
Y1 - 2021/7
N2 - Populations are typically defined as spatially contiguous sets of individuals, but large populations of social species can be composed of discrete social communities that often overlap in space. Masai giraffes (Giraffa camelopardalis tippelskirchi) of Tanzania live in distinct social subpopulations that overlap spatially, enabling us to simultaneously explore environmental and social factors correlated with demographic variation in a metapopulation of >1,400 adult females and calves. We considered statistically distinct communities in the social network as subpopulations and tested for variation among the 10 subpopulations in adult female survival, calf survival, and reproductive rate (calf-to-adult female ratio). We then related variation in demographic rates among subpopulations to differences in vegetation, soil type, proximity to 2 types of human settlements, local giraffe population density, and social metrics of relationship strength and exclusivity among adult females. We did not find any among-subpopulation effects on adult female survival, suggesting adult female survival is buffered against environmental heterogeneity among subpopulations. Variation in calf demographic rates among subpopulations were correlated with vegetation, soils, anthropogenic factors, and giraffe population density but not with adult female relationship metrics, despite substantial spatial overlap. Subpopulations with more dense bushlands in their ranges had lower calf survival probabilities, and those closer to human settlements had higher reproductive rates, possibly because of spatial gradients in natural predation. Reproductive rates were higher in subpopulations with more volcanic soils, and calf survival probabilities were greater in subpopulations with higher local adult female densities, possibly related to higher-quality habitat associated with fertile soils or lower predation risk, or to greater competitive ability. The variation in fitness among subpopulations suggests that giraffes do not move unhindered among resource patches to equalize reproductive success, as expected according to an ideal free distribution. The differences in calf survival and reproductive rates could rather indicate intercommunity differences in competitive ability, perception, learning, or experience. Our approach of comparing demography among spatially overlapping yet distinct socially defined subpopulations provides a biologically meaningful way to quantify environmental and social factors influencing fine-scale demographic variation for social species.
AB - Populations are typically defined as spatially contiguous sets of individuals, but large populations of social species can be composed of discrete social communities that often overlap in space. Masai giraffes (Giraffa camelopardalis tippelskirchi) of Tanzania live in distinct social subpopulations that overlap spatially, enabling us to simultaneously explore environmental and social factors correlated with demographic variation in a metapopulation of >1,400 adult females and calves. We considered statistically distinct communities in the social network as subpopulations and tested for variation among the 10 subpopulations in adult female survival, calf survival, and reproductive rate (calf-to-adult female ratio). We then related variation in demographic rates among subpopulations to differences in vegetation, soil type, proximity to 2 types of human settlements, local giraffe population density, and social metrics of relationship strength and exclusivity among adult females. We did not find any among-subpopulation effects on adult female survival, suggesting adult female survival is buffered against environmental heterogeneity among subpopulations. Variation in calf demographic rates among subpopulations were correlated with vegetation, soils, anthropogenic factors, and giraffe population density but not with adult female relationship metrics, despite substantial spatial overlap. Subpopulations with more dense bushlands in their ranges had lower calf survival probabilities, and those closer to human settlements had higher reproductive rates, possibly because of spatial gradients in natural predation. Reproductive rates were higher in subpopulations with more volcanic soils, and calf survival probabilities were greater in subpopulations with higher local adult female densities, possibly related to higher-quality habitat associated with fertile soils or lower predation risk, or to greater competitive ability. The variation in fitness among subpopulations suggests that giraffes do not move unhindered among resource patches to equalize reproductive success, as expected according to an ideal free distribution. The differences in calf survival and reproductive rates could rather indicate intercommunity differences in competitive ability, perception, learning, or experience. Our approach of comparing demography among spatially overlapping yet distinct socially defined subpopulations provides a biologically meaningful way to quantify environmental and social factors influencing fine-scale demographic variation for social species.
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U2 - 10.1002/jwmg.22044
DO - 10.1002/jwmg.22044
M3 - Article
AN - SCOPUS:85104044043
VL - 85
SP - 920
EP - 931
JO - Journal of Wildlife Management
JF - Journal of Wildlife Management
SN - 0022-541X
IS - 5
ER -