Characterizing gonadal and adrenal activity by fecal steroid analyses in pygmy rabbits (Brachylagus idahoensis).

In 2001, the sudden collapse of the Columbia Basin population of pygmy rabbits prompted the initiation of a captive breeding program to facilitate reintroduction, but reproductive success in captivity has not met expectations. Therefore, the objective of this study was to characterize the reproductive and adrenal endocrinology of this endangered rabbit species so that appropriate management strategies could be developed to monitor animal welfare and increase reproduction. Fecal samples were collected from 27 female pygmy rabbits over three breeding and non-breeding seasons. HPLC analyses verified the presence of progesterone in the excreta of pygmy rabbits, but the majority of progestagen metabolites were unidentified polar compounds. By contrast, >70% of glucocorticoid immunoactivity was associated with cortisol. Longitudinal fecal hormone profiles during pregnancy were characterized by a large spike in progestagens shortly after mating, a gradual increase in progestagen and glucocorticoid concentrations throughout gestation and a return of hormones to baseline soon after birth (Day 24). The spike in progestagens 1 day after mating was a significant discovery for this species and appears to provide a reliable means of determining if a successful mating has occurred. Seasonal analyses of hormone excretion found that progestagen baselines did not vary between the breeding and non-breeding seasons, but, as expected, were highest during the breeding season in association with pregnancy. Across seasons, the lowest concentrations of glucocorticoids were associated with the highest rates of offspring production and survival, suggesting a possible link between heightened adrenal activity and lowered reproductive fitness in pygmy rabbits.

AN EXPERIMENTAL STUDY OF THE EFFECTS OF CHEMICALLY DISPERSED OIL ON FEATHER STRUCTURE AND WATERPROOFING IN COMMON MURRES ( URIA AALGE).

Following an oil spill in the marine environment, chemical dispersants, which increase oil droplet formation and distribution into the water column, are assumed to provide a net benefit to seabirds by reducing the risk of exposure to oil on the water surface. However, few data are available regarding acute, external impacts of exposure to dispersed oil. We evaluated the effects of known concentrations of dispersant and crude oil in artificial seawater on live Common Murres ( Uria aalge). Waterproofing and microscopic feather geometry were evaluated over time and compared to pre-exposure values. Birds exposed to a high concentration of dispersant experienced an immediate, life-threatening loss of waterproofing and buoyancy, both of which resolved within 2 d. Birds exposed to oil, or a dispersant and oil mixture, experienced dose-dependent waterproofing impairment without resolution over 2 d. Alterations in feather geometry were observed in oil-exposed or dispersant- and oil-exposed birds and were associated with increased odds of waterproofing impairment compared to control birds. At a given contaminant concentration, there were no significant differences in waterproofing between oil-exposed and dispersant- and oil-exposed birds. We found that acute, external effects of oil and dispersed oil exposure are comparable and dose-dependent. Our results also indicate that a zero-risk assumption should not be used when seabirds are present within the dispersant application zone.

Ophthalmic effects of petroleum dispersant exposure on common murres (Uria aalge): An experimental study.

The safety of chemical dispersants used during oil spill responses is largely unknown in birds. We captured common murres in Monterey Bay, CA and exposed them to Corexit EC9500a, crude oil, or a combination in artificial seawater. We performed ophthalmic examinations and measured intraocular pressures and tear production before and after exposure. Loglinear analysis found that exposure to oil or dispersant was related to the development of conjunctivitis and corneal ulcers. Odds ratios for birds exposed to oil or dispersant were positive and significant for the development of conjunctivitis, while odds ratios for the development of corneal ulcers were positive and significant only for birds exposed to a high concentration of oil. Ocular exposure to dispersants and petroleum in seabirds may cause conjunctivitis and may play a role in the development of corneal ulcers. These results have implications for policymakers who develop protocols for the use of dispersants during marine oil spills.

Effects of genetic management on reproduction, growth, and survival in captive endangered pygmy rabbits (Brachylagus idahoensis).

A quarter of all lagomorph species worldwide are threatened with extinction. Captive breeding programs, such as that developed for the Columbia Basin (CB) pygmy rabbit (Brachylagus idahoensis), sometimes are implemented as emergency conservation measures to restore small, genetically distinct populations. However, small source populations also may have low genetic diversity, which may influence attributes related to fitness, including growth, survival, and reproduction. We used mixed-effects regression models to explore the influence of genetic pedigree (% CB) on pairing success, growth, and survival during the 10-year captive breeding program at Washington State University, which included controlled pairings and outbreeding with pygmy rabbits from Idaho. Pairing success, juvenile growth, and juvenile survival declined with increasing CB pedigree of 1 or both parents, suggesting inbreeding depression among the small number of related founders. Demographic variables such as age, sex, and previous pregnancies, and environmental variables such as month and temperature at birth also were associated with production of pygmy rabbits. Our study illustrates the difficulty of retaining a unique genome of a small source population while simultaneously producing enough rabbits for restoration into natural habitat as part of endangered species recovery programs.

Nutritional requirements and diet choices of the pygmy rabbit (Brachylagus idahoensis): a sagebrush specialist.

Sagebrush (Artemisia tridentata) comprises up to 99% of the winter and 50% of the summer diets of pygmy rabbits (Brachylagus idahoensis). Few animals specialize on such plants as sagebrush, which contain high levels of plant chemicals that can be toxic. We investigated the nutritional requirements of pygmy rabbits and their ability and propensity to consume sagebrush alone and as part of a mixed diet. We compared diet choices of pygmy rabbits with that of a generalist forager, the eastern cottontail (Sylvilagus floridanus). Pygmy rabbits had a moderately low nitrogen requirement (306.5 mg N/kg(0.75)/d), but a relatively high energy requirement, needing 750.8 kJ digestible energy/kg(0.75)/d to maintain their body mass while residing in small cages. They digested fiber in pelleted diets similarly to other small hindgut fermenters, but both cottontails and pygmy rabbits digested the fiber in sagebrush better than expected based on its indigestible acid detergent lignin content. Pygmy rabbits consumed more sagebrush than cottontails, regardless of the amount and nutritional quality of supplemental pellets provided. When consuming sagebrush alone, they ate barely enough to meet their energy requirements, whereas cottontails ate only enough sagebrush to meet 67% of theirs. Both rabbit species ate more sagebrush as the quality and quantity of supplemental pellets declined, and more greenhouse-grown sagebrush than sagebrush grown outside. Urine was more acidic when consuming sagebrush than when consuming pellets, indicating detoxification by the liver. Pygmy rabbits do not require sagebrush to survive, but seem to tolerate terpenes and other plant chemicals in sagebrush better than cottontails do.