Estimation of population density and investigation of socio-spatial organization of ocelots (Leopardus pardalis) from comparison and integration of two noninvasive methods

Rodgers, Torrey

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Description

Title

Estimation of population density and investigation of socio-spatial organization of ocelots (Leopardus pardalis) from comparison and integration of two noninvasive methods

Author(s)

Rodgers, Torrey

Issue Date

2014-05-30T16:46:53Z

Director of Research (if dissertation) or Advisor (if thesis)

• Heske, Edward J.
• Schooley, Robert L.

Department of Study

School of Integrative Biology

Discipline

Biology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Ocelots
• Leopardus pardalis
• noninvasive genetics
• camera trapping
• population density
• socio-spatial organization
• kin structure

Abstract

Due to their elusive nature, most carnivore species are difficult to monitor and study, and thus data are often insufficient to guide appropriate conservation action or to test hypotheses regarding species ecology (Nowell and Jackson 1996, Macdonald and Loveridge 2010, Rodgers and Janečka 2013). Among the 37 extant species in the family Felidae, 26 are listed as endangered, near threatened, or vulnerable, and over 86% have population numbers that are either decreasing or unknown (IUCN Red List 2011.2). The majority of felid species are secretive and solitary (Nowell and Jackson 1996, Sunquist and Sunquist 2002, Macdonald and Loveridge 2010), often making research based on visual observation impossible. Studying felids using traditional capture methods can be costly, labor intensive, or invasive. Telemetry studies yield the greatest level of information on behavior and ecology, however these methods require live capture that may cause stress and disturbance, or potentially injury or mortality if done improperly, raising ethical concerns (Greenwood 1996, Piggott and Taylor 2003, Kelly et al. 2012). Moreover, the significant effort or cost needed to track individuals via radio or GPS collars leads to few studies at a small number of sites, often with small sample sizes (Kelly et al. 2012). In response to these challenges, two noninvasive methods have become more commonplace in carnivore research: camera trapping (Carey 1926, Karanth 1995), and noninvasive genetics (Hoss et al. 1992, Kohn and Wayne 1997). These two methods do not require capture or direct observation of study animals, greatly increasing the amount of data that can be collected, while also alleviating some of the ethical concerns involved in animal capture. To date, most studies employing these techniques have examined species distributions or population abundance, while fewer have used them to study aspects of species ecology and behavior (Rodgers and Janečka 2013). The research contained in this thesis first compares the use of these two techniques for estimation of population density (chapter 1), and then integrates the two techniques to study aspects of species ecology and behavior (chapter 2) in ocelots (Leopardus pardalis) on Barro Colorado Island, Panama. Ocelots are a medium-sized felid that ranges from northern Argentina to the southern United States. Although ocelots are currently listed as least concern throughout their range (IUCN 2013), some populations (e.g. southern Texas) are critically endangered, and many populations are in decline due to habitat loss. Ocelots are an ideal species for use of noninvasive techniques because they are elusive and difficult to directly observe or capture. Additionally, they possess unique spot patterns that make it possible to identify individuals from camera trap photographs, and they use communal latrines, making it relatively easy to obtain scat samples for noninvasive genetic analyses. Barro Colorado Island is also an ideal study site, because it contains a population of ocelots that is relatively closed geographically, making it possible to include the entire population in analyses. In chapter 1, I compare camera trapping with noninvasive genetics for the estimation of ocelot population density. Camera trapping has been used extensively to estimate abundance and population density in many carnivore species, and is generally considered as a reliable technique (O'Connell et al. 2011, Foster and Harmsen 2012). Use of noninvasive genetics to estimate population density has been increasing, however, few studies have examined the accuracy and precision of these techniques by comparing them with more established methods (Rodgers and Janečka 2013). My goal was to evaluate the accuracy and precision of noninvasive genetics for estimating population density in elusive carnivores relative to estimates from camera trapping in the same study population during the same time period. I found that the two techniques were comparable, supporting the validity of noninvasive genetic techniques for estimating density in elusive species. In chapter two, I integrated camera trapping and noninvasive genetics to examine patterns of spatiotemporal overlap and kin structure in ocelots. Historically, small felids were considered territorial, with one or both sexes maintaining exclusive territories, and this pattern of spatial organization has been observed in some ocelot populations (Tewes 1986, Ludlow and Sunquist 1987, Laack 1991). Recent research, however; has revealed considerable flexibility in spatial organization among population of many felid species, possibly as a result of differences in ecological factors such as resource availability and population density (Sandell 1989, Goodrich et al. 2010). As the ocelot population on Barro Colorado Island is at extremely high density, I hypothesized that ocelots in this population would not maintain exclusive territories due to the high costs of defending a territory from many competitors. To examine spatiotemporal overlap between ocelots of both sexes, I used three years of camera-trap data encompassing the entire adult population. If individual ocelots overlap considerably in their use of space at high density, one mechanism that could reduce the cost of competition for shared resources is inclusive fitness (Hamilton 1964). To examine this possibility, I used noninvasive genetics to examine if individuals who overlapped in their use of space were more closely related than the population as a whole. I documented extensive intersexual and intrasexual overlap within both sexes of ocelots, however, intrasexual overlap between males was much stronger than between females. I also found a positive relationship between spatiotemporal overlap and genetic relatedness, supporting the hypothesis that kin structure plays a role in structuring ocelot spatial organization.

Graduation Semester

2014-05

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Copyright 2014 Torrey Rodgers

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