Development of an index of abundance for pygmy rabbit populations

Price, Amanda J.; Rachlow, Janet L.

doi:10.1002/jwmg.103

Cited by 16 publications

(17 citation statements)

References 36 publications

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“…In our system, pygmy rabbits were held at artificially high densities, well above the range described for wild populations. For example, Price and Rachlow (2011) documented a maximum density of 0.46 pygmy rabbits/ha in southeastern Idaho, compared with our range of 5-22 adult rabbits/ha. Consequently, these results should not be used to predict the response to changes in density of wild populations that are below carrying capacity.…”

Section: Reproductive Outputsupporting

confidence: 50%

Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph

DeMay

Becker

Waits

et al. 2016

Ecological Applications

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Understanding reproduction and mating systems is important for managers tasked with conserving vulnerable species. Genetic tools allow biologists to investigate reproduction and mating systems with high resolution and are particularly useful for species that are otherwise difficult to study in their natural environments. We conducted parentage analyses using 19 nuclear DNA microsatellite loci to assess the influence of population density, genetic diversity, and ancestry on reproduction, and to examine the mating system of pygmy rabbits (Brachylagus idahoensis) bred in large naturalized enclosures for the reintroduction and recovery of the endangered distinct population in central Washington, USA. Reproductive output for females and males decreased as population density and individual homozygosity increased. We identified an interaction indicating that male reproductive output decreased as genetic diversity declined at high population densities, but there was no effect at low densities. Males with high amounts (> 50%) of Washington ancestry had higher reproductive output than the other ancestry groups, while reproductive output was decreased for males with high northern Utah/Wyoming ancestry and females with high Oregon/Nevada ancestry. Females and males bred with an average of 3.8 and 3.6 mates per year, respectively, and we found no evidence of positive or negative assortative mating with regards to ancestry. Multiple paternity was confirmed in 81% of litters, and we report the first documented cases of juvenile breeding by pygmy rabbits. This study demonstrates how variation in population density, genetic diversity, and ancestry impact fitness for an endangered species being bred for conservation. Our results advance understanding of basic life history characteristics for a cryptic species that is difficult to study in the wild and provide lessons for managing populations of vulnerable species in captive and free-ranging populations.

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Section: Reproductive Outputsupporting

confidence: 50%

Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph

DeMay

Becker

Waits

et al. 2016

Ecological Applications

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“…(), who concluded that fresh sign could reliably index pygmy rabbit population trends. Indices of pygmy rabbit abundance have also been developed that are based on the density of active burrow systems, and have been found to be positively correlated with pygmy rabbit abundance (Price and Rachlow ). We used fresh pygmy rabbit sign to index trends across space rather than time, further negating any bias associated with temporal variation.…”

Section: Discussionmentioning

confidence: 99%

Relationships between gas field development and the presence and abundance of pygmy rabbits in southwestern Wyoming

et al. 2017

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Abstract. More than 5957 km 2 in southwestern Wyoming is currently covered by operational gas fields, and further development is projected through 2030. Gas fields fragment landscapes through conversion of native vegetation to roads, well pads, pipeline corridors, and other infrastructure elements. The sagebrush steppe landscape where most of this development is occurring harbors 24 sagebrush-associated species of greatest conservation need, but the effects of gas energy development on most of these species are unknown. Pygmy rabbits (Brachylagus idahoensis) are one such species. In 2011, we began collecting three years of survey data to examine the relationship between gas field development density and pygmy rabbit site occupancy patterns on four major Wyoming gas fields (Continental Divide-Creston-Blue Gap, Jonah, Moxa Arch, Pinedale Anticline Project Area). We surveyed 120 plots across four gas fields, with plots distributed across the density gradient of gas well pads on each field. In a 1 km radius around the center of each plot, we measured the area covered by each of 10 gas field infrastructure elements and by shrub cover using 2012 National Agriculture Imagery Program imagery. We then modeled the relationship between gas field elements, pygmy rabbit presence, and two indices of pygmy rabbit abundance. Gas field infrastructure elements-specifically buried utility corridors and a complex of gas well pads, adjacent disturbed areas, and well pad access roads-were negatively correlated with pygmy rabbit presence and abundance indices, with sharp declines apparent after approximately 2% of the area consisted of gas field infrastructure. We conclude that pygmy rabbits in southwestern Wyoming may be sensitive to gas field development at levels similar to those observed for greater sage-grouse, and may suffer local population declines at lower levels of development than are allowed in existing plans and policies designed to conserve greater sage-grouse by limiting the surface footprint of energy development. Buried utilities, gas well pads, areas adjacent to well pads, and well pad access roads had the strongest negative correlation with pygmy rabbit presence and abundance. Minimizing the surface footprint of these elements may reduce negative impacts of gas energy development on pygmy rabbits.

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“…; Gruber et al . ; Johnson , Funston et al., ; Price & Rachlow ; Bengsen et al . ; Keane, Jones & Milner‐Gulland ), based on the assumption that detection probabilities may be constant or can be controlled for in some manner.…”

Section: Introductionmentioning

confidence: 98%

“…The thrust of these criticisms was that predictions about population size from such indices are obscured by the variation in detection rates of the indexing method over time or space. Despite strong criticisms, attempts to calibrate indices directly against estimates of absolute densities have continued persistently since 2005 (see Gusset & Burgener 2005;Stephens et al 2006, Barea-Azc on et al 2007Gruber et al 2008;Johnson 2008, Funston et al, 2010Price & Rachlow 2011;Bengsen et al 2011;Keane, Jones & Milner-Gulland 2011), based on the assumption that detection probabilities may be constant or can be controlled for in some manner.…”

Section: Introductionmentioning

confidence: 99%

An examination of index‐calibration experiments: counting tigers at macroecological scales

et al. 2015

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Summary1. An index-calibration experiment involves rigorous estimation of animal abundance at a small scale to calibrate a less rigorously derived index of abundance. The efficacy of such index-calibration experiments has been a matter of much controversy. In this study, we develop theoretical models and test them with empirical data on large-scale index-calibration experiments on tigers Panthera tigris to advance our understanding of this controversy. 2. We propose two models that describe the sampling processes involved in typical index-calibration experiments. Using analytical derivations and some simulations, we evaluate the relative roles of these sampling parameters on the R 2 (coefficient of determination) statistic -a common inferential tool used in such calibration experiments. 3. We make predictions about the R 2 statistic using our theoretical derivations and estimates from large-scale occupancy surveys of tigers in India. We then compare our predictions with empirical estimates of two tiger sign index-calibration experiments (IC-Karanth and IC-Jhala). 4. Our theoretical models show that the R 2 statistic increases when individual-specific detection probability is high and is constant, increases when the variance-to-mean ratio of abundance increases, increases when precision of abundance estimates improves and declines when mean abundance increases. All predictions about the two index-calibration experiments showed a poor performance of the R 2 statistic (R 2 < 0Á40). Inference from ICKaranth was extremely poor (R 2 ¼ 0Á0004) and comparable to model predictions (P value = 0Á0754). Anomalously (P value < 0Á0001), inference from IC-Jhala was exceedingly high (R 2 ¼ 0Á95). 5. Our study shows that such direct index-calibration experiments using the R 2 statistic yield poor inferences unless all the sampling process parameters lie within a limited range. Ignoring the consequence of the effect of these parameters during survey design could result in expenditure of huge resources with little gain in ecological inference. Analysis using joint likelihood models, with appropriate survey designs, may be more fruitful than clinging on to such composite, direct R 2 -based models.

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Development of an index of abundance for pygmy rabbit populations

Cited by 16 publications

References 36 publications

Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph

Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph

Relationships between gas field development and the presence and abundance of pygmy rabbits in southwestern Wyoming

An examination of index‐calibration experiments: counting tigers at macroecological scales

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