Interspecific interactions between wild felids vary across scales and levels of urbanization

Abstract

Ongoing global landscape change resulting from urbanization is increasingly linked to changes in species distributions and community interactions. However, relatively little is known about how urbanization influences competitive interactions among mammalian carnivores, particularly related to wild felids. We evaluated interspecific interactions between medium- and large-sized carnivores across a gradient of urbanization and multiple scales. Specifically, we investigated spatial and temporal interactions of bobcats and pumas by evaluating circadian activity patterns, broad-scale seasonal interactions, and fine-scale daily interactions in wildland-urban interface (WUI), exurban residential development, and wildland habitats. Across levels of urbanization, interspecific interactions were evaluated using two-species and single-species occupancy models with data from motion-activated cameras. As predicted, urbanization increased the opportunity for interspecific interactions between wild felids. Although pumas did not exclude bobcats from areas at broad spatial or temporal scales, bobcats responded behaviorally to the presence of pumas at finer scales, but patterns varied across levels of urbanization. In wildland habitat, bobcats avoided using areas for short temporal periods after a puma visited an area. In contrast, bobcats did not appear to avoid areas that pumas recently visited in landscapes influenced by urbanization (exurban development and WUI habitat). In addition, overlap in circadian activity patterns between bobcats and pumas increased in exurban development compared to wildland habitat. Across study areas, bobcats used sites less frequently as the number of puma photographs increased at a site. Overall, bobcats appear to shape their behavior at fine spatial and temporal scales to reduce encounters with pumas, but residential development can potentially alter these strategies and increase interaction opportunities. We explore three hypotheses to explain our results of how urbanization affected interspecific interactions that consider activity patterns, landscape configuration, and animal scent marking. Altered competitive interactions between animals in urbanized landscapes could potentially increase aggressive encounters and the frequency of disease transmission.

Keywords: Bobcat; Lynx rufus; Puma concolor; competition; detection probability; mountain lion; occupancy; residential development; species interactions; urban gradient.

Figure 1

Interspecific interactions between the larger‐bodied puma (A) (typical adult weights range between 40 and 80 kg) and medium‐sized bobcat (B) (typical adult weights range between 7 and 12 kg) were evaluated across multiple levels of urbanization in Colorado, USA. Photographs were obtained from motion‐activated cameras in study areas.

Figure 2

Motion‐activated cameras were maintained across two study sites in Colorado, USA, exhibiting varying levels of urbanization. The more rural Western Slope (WS) was characterized by an exurban development southern grid and a wildland northern grid during 2009. The more urbanized Front Range (FR) study area was characterized by a wildland–urban interface (WUI) southern grid and wildland northern grid during 2010.

Figure 3

Overlap in activity patterns between bobcats and pumas was greater in exurban development compared to wildland habitat on the Western Slope (WS) during 2009 (A) and similar between wildland–urban interface (WUI) and wildland habitat on the Front Range (FR) during 2010 (B). Kernel density of activity is represented along the y‐axis and the 24‐h circadian daily cycle occurs along the x‐axis.

Figure 4

Bobcat daily detection probability estimates (with associated 95% confidence intervals) were lower for 2–3 days after a puma visited a site in wildland habitat on the Western Slope (A) and Front Range (B) of Colorado. Bobcat detection probability was evaluated in relation to 1‐ to 4‐day lag periods of puma detection at a site considering the interaction between grid (urbanized or wildland) and each lag effect of puma detection (P1 to P4) on bobcat detection probability using single‐species occupancy models.

Figure 5

Bobcat daily detection probability estimates (with associated 95% confidence intervals) in relation to puma detection in exurban development and wildland habitat on the Western Slope (WS) in 2009 (A) and wildland–urban interface (WUI) and wildland habitat on the Front Range (FR) in 2010 (B). Estimates are based on the interaction between grid and puma lag effect of 3 days on the WS (A) and the interaction between grid and puma lag effect of 2 days on the FR (B) using single‐species occupancy models.

Figure 6

The effect of pumas on daily detection probability of bobcats varied by puma use at a site. Bobcat detection probability decreased with the number of puma photographs at a camera location (i.e., puma count) on the Western Slope (WS) and Front Range (FR) of Colorado. Parameter estimates from the top models (Tables 5 and 6) were used to plot the relationship for puma count, human development (mean value), grid 1, puma lag effect (=0), and puma lag effect interaction (=0). Our data for the number of puma photographs at a site ranged from 0–8 images over 113 days on the WS and from 0–6 images over 92 days on the FR. Results are extrapolated to visualize the predicted response of bobcat detection probability in relation to higher frequencies of puma detections at a site.