Does Use of Backyard Resources Explain the Abundance of Urban Wildlife?

Abstract

While urbanization is clearly contributing to biodiversity loss, certain wildlife assemblages can paradoxically be diverse and abundant in moderately developed areas. One hypothesis to explain this phenomenon is that abundant anthropogenic resources for wildlife (i.e., food and shelter) outweigh the costs associated with urbanization. To test this hypothesis, we used camera traps to measure mammal species richness, diversity, and relative abundance (i.e., detection rate) in 58 residential yards in Raleigh, North Carolina, focusing on six types of features that might be used as resources: animal feeding, vegetable gardens, compost piles, chicken coops, brushpiles, and water sources. We also placed cameras at random control sites within each yard and sampled forests in nearby suburban and rural areas for comparison. We fit mixedeffects Poisson models to determine whether yard features, yard-scale characteristics, or landscape-scale landcover predicted mammal relative abundance for eight species. We also tested if the relative abundance of native canid predators in yards was related to the number of prey (rodents and lagomorphs). Species richness, diversity, and relative abundance of most mammal species was higher in yards and suburban forests than in rural forests. Within a yard, purposeful feeding had the strongest effect on animal relative abundance, with eastern gray squirrels (Sciurus carolinensis) being the most common (32.3 squirrels/day at feeders; 0.55 at control sites; 0.29 in suburban forests; and 0.10 in rural forests). We observed species using (e.g., eating) most yard features, although canids were less likely than other taxa to use resources in yards. The presence of a yard feature did not strongly affect the abundance of species at the control site in the yard, suggesting the influence of these features was highly localized. The relative abundance of predators had a positive association with prey relative abundance, and predators were less common in yards with fences. These results demonstrate that there is high use of anthropogenic resources, especially supplemental feeding by urban wildlife, and this increase in prey species may then attract predators, which supports the hypothesis that use of supplemental food resources explains the abundance of urban wildlife.

The effect of urbanization on spatiotemporal interactions between gray foxes and coyotes

“…If coyotes in suburban areas are less territorial, they may be a lower risk to gray foxes (i.e., Moll et al, 2018) and/or their movements might be less predictable (Ward, 2017), and thus do not provoke the same avoidance behaviors as rural coyotes. Alternatively, suburban forests, although fragmented, may offer resources abundant and/or clustered enough to facilitate coexistence between these species (Bateman & Fleming, 2012; Hansen et al, 2020).…”

Spatiotemporal interactions of a novel mesocarnivore community in an urban environment before and during SARS‐CoV‐2 lockdown

“…On average, garden characteristics were more important for species’ use intensity of the study area. Gardens have been found in another study to sustain the urban mammal communities specifically by maintaining high populations of prey species such as small rodents, and therefore attracting carnivore species (Hansen et al., 2020 ). For foxes, urban characteristics were more important for their presence; this may mean that the large‐scale variables affected whether or not they would go in gardens, while the garden characteristics at small scales would influence their use intensity, displaying a hierarchy between garden selection and use (Harris & Rayner, 1986 ; Rotenberry, 1985 ).…”

Gray squirrels consume anthropogenic food waste most often during winter

“…Urban development is a major form of land change, and can result in local extinction of native species and their replacement with non-native species (McKinney 2006 , 2008 ; Grimmond 2007 ; Grimm et al 2008 ). While some species, such as many carnivores (Ordeñana et al 2010 ), avoid urban environments, synanthropic species, for example, many bird and rodent species, manage to reproduce and persist in anthropogenically modified habitats (McKinney 2006 ; Hansen et al 2020 ). However, numerous sub-lethal effects on behavior, communication, metabolism, nutrition, stress hormone levels and health have been described (Birnie-Gauvin et al 2016 ).…”

“…Urban habitats differ in many aspects from more natural habitats. Importantly, they often present animals with predictable and abundant anthropogenic food subsidies in the form of bird feeders, nuts provided for rodents, backyard resources, composts, human food waste or refuse (Oro et al 2013 ; Plaza and Lambertucci 2017 ; Hansen et al 2020 ). Numerous urban populations of birds, mammals, reptiles and amphibians are known to consume anthropogenic food sources (Contesse et al 2004 ; Oro et al 2013 ; Birnie-Gauvin et al 2016 ; Plaza and Lambertucci 2017 ; Katlam et al 2018 ; Schulte-Hostedde et al 2018 ; Lenzi et al 2019 ).…”