Figure 2 - uploaded by Michael J Noonan
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The distribution of mammalian movement data. In (A), the GPS locations of 1,396 prey (blue) and predatory (orange) mammals across 62 species are plotted on the global map of Normalized Difference Vegetation Index ranging from low (-1) to high (1) productivity; and (B) shows the median ballistic length scales, lv, for each species.
Source publication
Animals moving through landscapes need to strike a balance between finding sufficient resources to grow and reproduce while minimizing encounters with predators. Because encounter rates are determined by the average distance over which directed motion persists, this trade-off should be apparent in individuals’ movement. Using GPS data from 1,396 in...
Citations
... Predator functional responses (i.e., foraging efficiency) are driven by predator searching and handling times, the former of which is influenced by the rate that predators encounter prey. Theoretical predictions and results from simple model systems indicate predators increase encounter rates when they make directed (or ballistic) movements compared with sinuous movements (Bartumeus et al., 2008;Noonan et al., 2023;Visser & Kiørboe, 2006). Thus, the addition of linear features to a landscape should theoretically increase predator encounter rates with prey by facilitating directed movements. ...
Humans are increasingly recognized as important players in predator–prey dynamics by modifying landscapes. This trend has been well‐documented for large mammal communities in North American boreal forests: logging creates early seral forests that benefit ungulates such as white‐tailed deer (Odocoileus virginianus), while the combination of infrastructure development and resource extraction practices generate linear features that allow predators such as wolves (Canis lupus) to travel and forage more efficiently throughout the landscape. Disturbances from recreational activities and residential development are other major sources of human activity in boreal ecosystems that may further alter wolf–ungulate dynamics. Here, we evaluate the influence that several major types of anthropogenic landscape modifications (timber harvest, linear features, and residential infrastructure) have on where and how wolves hunt ungulate neonates in a southern boreal forest ecosystem in Minnesota, USA. We demonstrate that each major anthropogenic disturbance significantly influences wolf predation of white‐tailed deer fawns (n = 427 kill sites). In contrast with the “human shield hypothesis” that posits prey use human‐modified areas as refuge, wolves killed fawns closer to residential buildings than expected based on spatial availability. Fawns were also killed within recently‐logged areas more than expected. Concealment cover was higher at kill sites than random sites, suggesting wolves use senses other than vision, probably olfaction, to detect hidden fawns. Wolves showed strong selection for hunting along linear features, and kill sites were also closer to linear features than expected. We hypothesize that linear features facilitated wolf predation on fawns by allowing wolves to travel efficiently among high‐quality prey patches (recently logged areas, near buildings), and also increase encounter rates with olfactory cues that allow them to detect hidden fawns. These findings provide novel insight into the strategies predators use to hunt ungulate neonates and the many ways human activity alters wolf–ungulate neonate predator–prey dynamics, which have remained elusive due to the challenges of locating sites where predators kill small prey. Our research has important management and conservation implications for wolf–ungulate systems subjected to anthropogenic pressures, particularly as the range of overlap between wolves and deer expands and appears to be altering food web dynamics in boreal ecosystems.
Direct encounters, in which two or more individuals are physically close to one another, are a topic of increasing interest as more and better movement data become available. Recent progress, including the development of statistical tools for estimating robust measures of changes in animals’ space use over time, facilitates opportunities to link direct encounters between individuals with the long-term consequences of those encounters. Working with movement data for coyotes (Canis latrans) and grizzly bears (Ursus arctos horribilis), we investigate whether close intraspecific encounters were associated with spatial shifts in the animals’ range distributions, as might be expected if one or both of the individuals involved in an encounter were seeking to reduce or avoid conflict over space. We analyze the movement data of a pair of coyotes in detail, identifying how a change in home range overlap resulting from altered movement behavior was apparently a consequence of a close intraspecific encounter. With grizzly bear movement data, we approach the problem as population-level hypothesis tests of the spatial consequences of encounters. We find support for the hypotheses that (1) close intraspecific encounters between bears are, under certain circumstances, associated with subsequent changes in overlap between range distributions and (2) encounters defined at finer spatial scales are followed by greater changes in space use. Our results suggest that animals can undertake long-term, large-scale spatial changes in response to close intraspecific encounters that have the potential for conflict. Overall, we find that analyses of movement data in a pairwise context can (1) identify distances at which individuals’ proximity to one another may alter behavior and (2) facilitate testing of population-level hypotheses concerning the potential for direct encounters to alter individuals’ space use.
The long‐term conservation of species at risk relies on numerous, and often concurrent, management actions to support their recovery. Generally, these actions are habitat‐based while others are focused on a species' position within its ecological community. Less studied are the impacts from human presence, despite evidence that human activity may reduce the area functionally available for occupancy or resource acquisition. In the winter of 2020/2021, COVID‐19‐related travel restrictions led to a reduction in helicopter‐assisted back‐country skiing (heli‐skiing). We examined how these reductions in heli‐skiing (termed the anthropause) affected the movement ecology and resource selection of southern mountain caribou (Rangifer tarandus caribou) as compared to two prior years (2018/2019 and 2019/2020) and the following year when heli‐skiing resumed (2021/2022). We found that home‐range size was on average 80–120% larger during the anthropause than in years of normal heli‐ski operations. Movement rates also varied among periods, with movement during the anthropause (11.9 km²/day) being higher than in 2019/2020 (7.8 km²/day) and 2021/2022 (8.7 km²/day), though similar to 2018/2019 (12.2 km²/day). Resource selection among periods did not differ, with caribou consistently selecting old forests, high elevations and gentle terrain. These results suggest that back‐country recreation, specifically heli‐skiing, may be limiting access to resources for southern mountain caribou. This limitation arises through reduced home‐range size within suitable late‐winter habitat, relative to when heli‐skiing is reduced or not occurring – consistent with Encounter Theory. While the demographic effects of reduced home‐range size and movement were not examined here, reduced access to resources likely compounds other stressors known to affect population viability of caribou. The results of this study demonstrate the impact that recreation can have on wildlife and highlight the need to consider heli‐skiing and other forms of recreation when developing recovery plans.
