Krista L. Jones

Sudden Increase in a Rare Endemic Carnivore: Ecology of the Island Spotted Skunk

Abstract The island spotted skunk (Spilogale gracilis amphiala), an insular endemic carnivore, recently increased unexpectedly from rarity to abundance on Santa Cruz Island, California. Two explanations have been proposed for this striking increase: competitive release due to decline of the island fox (Urocyon littoralis santacruzae) and vegetative recovery due to removal of feral livestock. To examine the causes and consequences of the increase, we assessed abundance, body mass, home-range size, spatial resource use (den sites and habitat use), temporal resource use, and diet of island spotted skunks during abundance in 2003–2004 and compared it with similar measures during rarity in 1992. Capture success of skunks increased exponentially from 1992 to 2004 (r = 0.38), leading to extraordinarily high densities (9–19 individuals/km2). Both body mass and home-range size remained unchanged, suggesting that per capita resource abundance was not higher in 2003–2004 compared to 1992. We found modest shifts in habitat use, diet, and possibly diurnal activity, providing some support for release from exploitative competition as an explanation for the increase. However, there was a marked shift in den selection, toward unprotected dens and away from multiple use, that is not likely attributable to either release from exploitative competition or to island recovery. Thus, our results suggest that, although both of these processes have likely played a role, release from interference competition also may be a factor behind the dramatic increase in number of skunks. Skunks on Santa Cruz Island may be nearing or even exceeding carrying capacity, and the future of the population and its effects on the endangered island fox remain unclear.

Genetic differentiation of island spotted skunks, Spilogale gracilis amphiala

Abstract The island spotted skunk (Spilogale gracilis amphiala) is endemic to the 2 largest California Channel Islands, Santa Cruz and Santa Rosa. Unlike the island fox (Urocyon littoralis) and island subspecies of the deer mouse (Peromyscus maniculatus), the island spotted skunk shows no morphological differentiation between islands and is differentiated only weakly from mainland subspecies, suggesting recent colonization. However, the islands have been isolated from each other and the mainland throughout the Quaternary Period. We used 8 microsatellite loci to investigate the distribution of genetic variation within and among populations of spotted skunks from 8 localities (the 2 islands and 6 mainland localities), representing 4 subspecies. Tissue samples were obtained from 66 fresh specimens collected from 2000 to 2002 and 142 museum specimens collected from 1906 to 1994. Allelic richness and heterozygosity in island spotted skunk populations was approximately 30% lower than that found in mainland localities or subspecies. All localities or subspecies were significantly differentiated (mean FST was 0.17 and 0.13 for localities and subspecies, respectively). Contrary to comparisons based on morphological data, genetic differentiation was especially strong between islands and between island and mainland localities or subspecies. Patterns of differentiation suggest that skunks colonized the Channel Islands shortly before rising sea levels separated Santa Cruz and Santa Rosa islands (11,500 years ago). Our results indicate that the taxonomic status of the island spotted skunk should be reconsidered and that both island populations might constitute evolutionarily significant units worthy of conservation.

Host stress physiology and Trypanosoma haemoparasite infection influence innate immunity in the woylie (Bettongia penicillata)

Understanding immune function is critical to conserving wildlife in view of infectious disease threats, particularly in threatened species vulnerable to stress, immunocompromise and infection. However, few studies examine stress, immune function and infection in wildlife. We used a flow cytometry protocol developed for human infants to assess phagocytosis, a key component of innate immunity, in a critically endangered marsupial, the woylie (Bettongia penicillata). The effects of stress physiology and Trypanosoma infection on phagocytosis were investigated. Blood and faecal samples were collected from woylies in a captive facility over three months. Trypanosoma status was determined using PCR. Faecal cortisol metabolites (FCM) were quantified by enzyme-immunoassay. Mean phagocytosis measured was >90%. An interaction between sex and FCM influenced the percentage of phagocytosing leukocytes, possibly reflecting the influence of sex hormones and glucocorticoids. An interaction between Trypanosoma status and FCM influenced phagocytosis index, suggesting that stress physiology and infection status influence innate immunity.

Evaluation of a ferret-specific formula for determining body surface area to improve chemotherapeutic dosing

OBJECTIVE To use CT-derived measurements to create a ferret-specific formula for body surface area (BSA) to improve chemotherapeutic dosing. ANIMALS 25 adult ferrets (19 live and 6 cadavers). PROCEDURES Live subjects were weighed, and body measurements were obtained by each of 3 observers while ferrets were awake and anesthetized. Computed tomography was performed, and a 3-D surface model was constructed with open-source imaging software, from which BSA was estimated. The CT-derived values were compared with BSA calculated on the basis of the traditional tape method for 6 cadavers. To further validate CT analysis software, 11 geometric shapes were scanned and their CT-derived values compared with those calculated directly via geometric formulas. Agreement between methods of surface area estimation was assessed with linear regression. Ferret-specific formulas for BSA were determined with nonlinear regression models. RESULTS Repeatability among the 3 observers was good for all measurements, but some measurements differed significantly between awake and anesthetized ferrets. Excellent agreement was found between measured versus CT-derived surface area of shapes, traditional tape- versus CT-derived BSA of ferret cadavers, and CT-derived BSA of cadavers with and without monitoring equipment. All surface area formulas performed relatively similarly. CONCLUSIONS AND CLINICAL RELEVANCE CT-derived BSA measurements of ferrets obtained via open-source imaging software were reliable. On the basis of study results, the recommended formula for BSA in ferrets would be 9.94 × (body weight)(2/3); however, this represented a relatively minor difference from the feline-derived formula currently used by most practitioners and would result in little practical change in drug doses.

Hematology, Serum Chemistry, and Serum Protein Electrophoresis Ranges for Free-ranging Roe Deer (Capreolus capreolus) in Sweden

Abstract We present the first reference ranges for hematology (n = 35 animals), serum biochemistry (n = 62), and serum protein electrophoresis (n = 32) in physically restrained free-ranging roe deer (Capreolus capreolus). Animals were captured in box traps and physically restrained for blood sampling during the winter in Sweden, 2011–13. No clinically significant sex or age differences were found.

Spatial and Genetic Organization of the Island Spotted Skunk, Spilogale gracilis amphiala

Abstract We assessed the spatial and genetic organization of the island spotted skunk (Spilogale gracilis amphiala) on Santa Cruz Island, California. Home ranges of adults were largely non-overlapping, consistent with expectations for a solitary species. Contrary to expectations, we found no evidence of a matrilineal spatial structure. Relatedness of adult females was not negatively correlated with geographic distance, nor was it positively correlated with overlap of home ranges, possibly because of excessive dispersal caused by exceptionally high densities. We did find evidence of a patrilineal structure at one study site, where relatedness among males was negatively correlated with distance. The explanation for differences between males and females in genetic structure is uncertain, but it may reflect the differential influence of high density on dispersal of males and females.

Social networks: a tool for assessing the impact of perturbations on wildlife behaviour and implications for pathogen transmission

Wildlife are increasingly subject to perturbations, which can impact pathogen transmission and lead to disease emergence. While a myriad of factors influence disease dynamics in wildlife, behaviour is emerging as a major influence. In this review, we examine how perturbations alter the behaviour of individuals and how, in turn, disease transmission may be impacted, with a focus on the use of network models as a powerful tool. There are emerging hypotheses as to how networks respond to different types of perturbations. The broad effects of perturbations make predicting potential outcomes and identifying mitigation opportunities for disease emergence critical; yet, the current paucity of data makes identification of underlying trends difficult. Social network analysis facilitates a mechanistic approach to how perturbation-induced behavioural changes result in shifts in pathogen transmission. However, the field is still developing, and future work should strive to address current deficits. There is particular need for empirical data to support modelling predictions and increased inclusion of pathogen monitoring in network studies.

Severe Hypoxemia in Muskoxen ( Ovibos moschatus ) Immobilized with Etorphine and Xylazine Corrected with Supplemental Nasal Oxygen.

Abstract Twenty-three muskoxen (Ovibos moschatus) housed in a captive facility for rewilding in Sweden were chemically immobilized for annual health evaluations and hoof trimming. The muskoxen were darted in May to September (2012–15) in their holding pen with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) intramuscularly. Twenty-two of the 23 animals were immobilized with a single dart injection. The mean (SD) induction time was 4 (2) min. Arterial blood gases were collected from 18 animals. All animals were severely hypoxemic with varying degrees of respiratory acidosis. The hypoxemia resolved in 17 of 18 animals with intranasal oxygen supplementation at 1 L/min per 100 kg. Relative arterial oxygen saturation (SpO2) measured by pulse oximetry was significantly higher than the arterial oxygen saturation calculated from the partial pressure of arterial oxygen (SaO2) obtained by a blood gas analyzer. Based on these findings, muskox can be immobilized successfully with etorphine (0.015 mg/kg) and xylazine (0.1 mg/kg) but should receive supplemental oxygen.

Wildlife in the line of fire: evaluating the stress physiology of a critically endangered Australian marsupial after bushfire

Abstract. Australian native fauna are thought to be well adapted to fire-prone landscapes, but bushfires may still pose considerable challenges or stressors to wildlife. We investigated the impact of bushfire on the stress physiology of the woylie (brush-tailed bettong, Bettongia penicillata) a critically endangered Australian marsupial, and assessed whether fitness indices (body condition and parasite load) influenced stress physiology before and after the fire. We hypothesised that there would be a significant change in stress physiology indicators (in the form of faecal cortisol metabolites, FCM) following the fire, compared with the months previous. We trapped woylies (n = 19) at Whiteman Park Reserve in Perth, Western Australia, two days after a major bushfire and measured FCM concentration by enzyme immunoassay. Population-level comparisons of FCM were made between these samples and those collected in previous months (n = 58). While mean FCM varied by month of sample collection, it was not higher after the fire. We suggest that woylies may be able to maintain homeostasis through change (allostasis), at least in the period immediately after the fire. This is supported by our finding that FCM did not relate significantly to body condition or parasite load. Our results potentially highlight the physiological and behavioural adaptations of woylies to fire, which could be further explored in future studies.