Density dependence or climatic variation? Factors influencing survival, recruitment, and population growth rate of Virginia opossums

Troyer, Elizabeth M.; Devitt, Susan E. Cameron; Sunquist, Melvin E.; Goswami, Varun R.; Oli, Madan K.

doi:10.1644/13-mamm-a-164.1

Cited by 14 publications

(8 citation statements)

References 56 publications

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“…Consistent with our hypothesis, male raccoons had lower apparent survival and higher recruitment, probably due to the permanent immigration and emigration of males to and from the study area associated with natal and breeding dispersal. The same pattern has been found for Virginia opossums ( Didelphis virginiana ) in this system, an ecologically similar mesopredator species that also exhibits male-biased natal and breeding dispersal [43] . In other mesopredator populations, sex differences in survival are often not present.…”

Section: Discussionsupporting

confidence: 79%

“…The same pattern has been found for Virginia opossums ( Didelphis virginiana ) in this system, an ecologically similar mesopredator species that also exhibits male-biased natal and breeding dispersal [43]. In other mesopredator populations, sex differences in survival are often not present.…”

Section: Discussionsupporting

confidence: 78%

“…In contrast, a sympatric population of Virginia opossums showed monthly variation in population growth rate and recruitment, strong covariation between these parameters, and a positive association of these parameters with precipitation variability (coefficient of variation of rainfall) [43]. While opossums and raccoons are ecologically similar as mesopredators, they follow different life history strategies–opossums live a faster life, with rapid reproduction and early senescence; raccoons live a slower life, with smaller litters spaced over longer lifespans [27].…”

Section: Discussionmentioning

confidence: 97%

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Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon

et al. 2014

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Populations of mesopredators (mid-sized mammalian carnivores) are expanding in size and range amid declining apex predator populations and ever-growing human presence, leading to significant ecological impacts. Despite their obvious importance, population dynamics have scarcely been studied for most mesopredator species. Information on basic population parameters and processes under a range of conditions is necessary for managing these species. Here we investigate survival, recruitment, and population growth rate of a widely distributed and abundant mesopredator, the northern raccoon (Procyon lotor), using Pradel’s temporal symmetry models and >6 years of monthly capture-mark-recapture data collected in a protected area. Monthly apparent survival probability was higher for females (0.949, 95% CI = 0.936–0.960) than for males (0.908, 95% CI = 0.893–0.920), while monthly recruitment rate was higher for males (0.091, 95% CI = 0.078–0.106) than for females (0.054, 95% CI = 0.042–0.067). Finally, monthly realized population growth rate was 1.000 (95% CI = 0.996–1.004), indicating that our study population has reached a stable equilibrium in this relatively undisturbed habitat. There was little evidence for substantial temporal variation in population growth rate or its components. Our study is one of the first to quantify survival, recruitment, and realized population growth rate of raccoons using long-term data and rigorous statistical models.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 97%

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Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon

et al. 2014

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“…This compensatory effect is conditioned on high reproduction capacity (i.e., large maximal litter size). Density‐dependent periodic recruitment typifies large herbivores (Gaillard et al ) but also represents a variety of medium‐size mammalian species such as the 3 species we examined here (Windberg , Hanson et al , Servanty et al , Troyer et al , Wolfe et al ). Although animals characterized by a maximal yearly litter size of 1–3 (medium‐size ungulates and the majority of large mammals) are predicted to be rather sensitive to harvesting, some medium‐size species that have maximal yearly litter sizes of 4–6 are predicted to show resilience to harvesting.…”

Section: Discussionmentioning

confidence: 99%

Unequal density dependence between survival and recruitment affects harvesting effectivness

Kapota

Saltz

2018

J Wildl Manag

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Recruitment and adult‐mortality may respond differently to increased population density. Such unequal density dependence (UDD) is evident for large mammals showing density dependence mainly in recruitment (reproduction rate or juvenile survival), whereas adult survival is high and varies little with density. Mechanistically, UDD is likely influenced by an unequal allocation of resources toward reproduction versus survival. Unequal density dependence is expected to affect compensation abilities, and hence may have serious implications with regard to population harvesting. We modeled UDD by linking population size to reproduction and survival through per capita resource availability and consumption. We integrated UDD into 2 population models (continuous vs. periodic recruitment) and investigated how it affected the compensatory dynamics of populations. For a population with continuous recruitment, our model predicted that although UDD stabilizes the population dynamics, it makes populations more vulnerable to harvesting as a consequence of lower compensatory ability, regardless of whether more resources are allocated to reproduction or to survival. For populations with periodic recruitment, on the other hand, an asymmetric effect of UDD is predicted. Strong density dependence in recruitment relative to adult survival yields a strong compensatory response, whereas equal or stronger density dependence in adult survival relative to recruitment yields weaker compensatory responses. Stronger density dependence in recruitment also causes the periodic fluctuations in population size to be amplified rather than dampened under harvesting. These results are robust to alternative model formulations (e.g., Ricker and Beverton‐Holt equations). Using an empirical example for coyotes (Canis latrans), wild boars (Sus scrofa), and white‐tailed deer (Odocoileus virginianus), we demonstrated the implications of our results for harvest management of medium‐size mammalian species that are periodic breeders and exhibit density‐dependent recruitment. Accounting for UDD in the population model of coyotes and wild boars, which are characterized by large litters, predicts compensation that is stronger than the response obtained without UDD. For white‐tailed deer, which are characterized by substantially smaller litters, accounting for UDD does not change the outcome. Harvest‐based control attempts of medium‐size mammals may hence be much less effective than predicted when the population models used to estimate them ignore UDD, suggesting the necessity of integrating UDD into these models. © 2018 The Wildlife Society.

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“…However, studies of the spatiotemporal dynamics of raccoon populations have been hindered by the lack of multiple long-term population time series (Gehrt 2002). Despite the critical roles, few studies have investigated the density dependence of mesocarnivores compared to large herbivores and small mammals (Troyer et al 2014a). Little was known regarding the population ecology of raccoons (Troyer et al 2014b).…”

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confidence: 99%

Spatiotemporal dynamics of mesocarnivore populations

Xingan

Wang²

2018

Wildlife Biology

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Density dependence or climatic variation? Factors influencing survival, recruitment, and population growth rate of Virginia opossums

Cited by 14 publications

References 56 publications

Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon

Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon

Unequal density dependence between survival and recruitment affects harvesting effectivness

Spatiotemporal dynamics of mesocarnivore populations

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