The Ecology Of Desert Bighorn Sheep Ovis Canadensis In The Peninsular Ranges Of California

Author : Sean Clemenza
Publisher :
ISBN 13 : 9781369795745
Total Pages : pages
Book Rating : 4.7/5 (957 download)

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Download or read book Pumas of the Peninsular Ranges written by Sean Clemenza and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: By the early 2000s, desert bighorn sheep (Ovis canadensis) populations in the southern California had declined significantly. These declines progressed to the point that bighorn sheep in the Peninsular Ranges population were listed as federally endangered in 1998 and these sheep became a California “Fully Protected Mammal” species (US Fish and Wildlife Service 1998, California Fish and Game 2016). Initially, high lamb mortality and low recruitment were thought to be responsible for the declines, however the most frequent cause of sheep mortality turned out to be predation by pumas (Puma concolor). In a local study, pumas were found to be the cause of death for 69% of all mortalities (Hayes et al. 2000). Predation at these levels could potentially impact population viability and persistence of bighorn sheep (Festa-Bianchet et al. 2006). Additionally as many bighorn sheep had been marked (e.g. collars and ear tags) for study and conservation, concerns were expressed over whether or not the marking made sheep more “conspicuous” and thus susceptible to predation (Rominger and Weisenberger 2000). During the course of investigating the possible impacts of marking bighorn sheep, I observed a unique regionally variable behavior of pumas, which is little studied and poorly understood. The behavior was that of pumas apparently abandoning kills temporarily to use remote day beds >2 km away. After remaining at day beds, pumas returned to feed at kill sites before repeating a similar process the next day. In order to better study the unique behavior, a new method was developed to detect remote day bed use. The new method is more widely applicable than to just puma behavior and has implications for central-place foraging analyses. Given utility of the new method in optimal foraging approaches, I examined optimality of puma foraging in a manner not done before. I compared my observations to predictions of the Marginal Value Theorem (Charnov 1976). My primary research objectives were to (1) test for differential selection in pumas preying on radio-collared versus uncollared bighorn sheep, (2) examine puma movement and behavior at and around kill sites, (3) develop a method to identify and examine puma kills in a way that allows central-place behaviors and specifically day bed use to be considered, (4) test predictions of the Marginal Value Theorem (MVT) for pumas and prey. As I described in chapter 1 (formatted for BioMed Central Research Notes) during biennial helicopter surveys from 2000-2004 in southern California, the total number of bighorn sheep in 5 of 8 recognized subpopulations of the Peninsular Ranges (Rubin et al. 1998) were estimated. The number of marked (radio-collared) bighorn sheep was subtracted from the total population to determine the number unmarked (uncollared). I used Global Positioning System (GPS) locations from pumas radio-collared between 2002-2004 to identify kills of pumas preying upon these bighorn sheep. Three pumas killed 23 bighorn sheep (19 uncollared and 4 radio-collared) over the course of the study. Pumas did not preferentially prey on marked versus unmarked bighorn sheep. Predation occurred primarily during crepuscular and nighttime hours, and 22 kill sites were identified by the occurrence of 2 or more consecutive puma GPS locations (a cluster) within 200 m of each other at 1900, 0000, and 0600 h. I tested the "conspicuous individual hypothesis" and found that there was no difference in puma predation upon radio- collared or uncollared bighorn sheep. Pumas tended to move long distances before and after kills, but their movement patterns immediately post-kill were much more restricted. Researchers can exploit this behavior to identify puma kill sites and investigate prey selection by designing studies, which detect puma locations spatially clustered between dusk and dawn. I developed a new method discussed in chapter 2 (formatted for the Journal of Wildlife Management), the first to account for day bed use behavior in pumas, which is widely applicable and can be used to identify central-place uses and behaviors away from central-places for a broad spectrum of taxa using location data. I developed the method to detect central-place use via GPS location clusters. Specifically, the method was designed to detect behaviors at clusters, such as remote day bed use. The method was validated and tested for puma kill/cache detection. This study is the first to account for the observed behavior during puma feeding of departing from and returning to caches. In the course of this study, I also documented the first long-term reuse of caches by pumas; and detected sex-based effects in foraging behavior. Overall, this study provided a unique approach to examine GPS location clusters in a way, which allows for analysis of central-place behaviors like day bed use. My results demonstrate that investing in new approaches to analysis can yield insight into regionally variable and difficult to observe behaviors, which is valuable to wildlife management. As described in chapter 3 (formatted for the Journal of Wildlife Management), optimal foraging is a key tenet of ecology and fundamental to our understanding of predator-prey interactions. The classical marginal value theorem (MVT) uses travel time between patches and patch quality to determine optimal patch residence time. While the MVT has been successfully tested in controlled laboratory environments, it has been insufficiently evaluated under natural conditions such as terrestrial predator and multi-prey systems. Using novel analytical techniques and data from long-term studies of pumas (Puma concolor), I found qualitative support for 2 of 3 MVT predictions tested. I found time spent at caches increased with increasing average foodivvalue (habitat quality) of caches. Time spent at caches also increased significantly for higher food value (quality) caches than lower food value caches. During my examination, I also detected sex-based effects in patch quality on foraging behavior. Overall, this study provided a unique approach to examine the MVT in the context of a complex natural predator-prey system. It also improved our understanding of behavior and highlighted some important new differences between sexes in pumas, which could convey both impacts to prey and benefits to scavengers. My results demonstrate that leveraging technological advances, such as in puma cache detection, with novel theoretical applications of field observations drives new understanding of cryptic behaviors such as those of ambush predators like pumas and is valuable to long-term and large- scale management.