Wild carnivores in zoos, conservation breeding centres, and farms commonly live in relatively small, unstimulating enclosures. Under these captive conditions, in a range of species including giant pandas, black-footed ferrets, and European mink, male reproductive abilities are often poor. Such problems have long been hypothesized to be caused by these animals' housing conditions. We show for the first time that rearing under welfare-improving (i.e., highly valued and stress-reducing) environmental enrichments enhances male carnivores' copulatory performance: in mate choice competitions, enriched male American mink (Neovison vison) mated more often than non-enriched males. We screened for several potential mediators of this effect. First was physiological stress and its impact on reproductive physiology; second, stress-mediated changes in morphology and variables related to immunocompetence that could influence male attractiveness; and third, behavioural changes likely to affect social competence, particularly autistic-like excessive routine and repetition (‘perseveration’) as is reflected in the stereotypies common in captive animals. Consistent with physiological stress, excreted steroid metabolites revealed that non-enriched males had higher cortisol levels and lower androgen levels than enriched conspecifics. Their os penises (bacula) also tended to be less developed. Consistent with reduced attractiveness, non-enriched males were lighter, with comparatively small spleens and a trend to greater fluctuating asymmetry. Consistent with impaired social competence, non-enriched males performed more stereotypic behaviour (e.g., pacing) in their home cages. Of all these effects, the only significant predictor of copulation number was stereotypy (a trend suggesting that low bodyweights may also be influential): highly stereotypic males gained the fewest copulations. The neurophysiological changes underlying stereotypy thus handicap males sexually. We hypothesise that such males are abnormally perseverative when interacting with females. Investigating similar problems in other taxa would be worthwhile, since many vertebrates, wild and domestic, live in conditions that cause stereotypic behaviour and/or impair neurological development.
A series of toxicity tests were conducted to assess the effects of low to moderate exposure to artificially weathered Deepwater Horizon Mississippi Canyon 252 crude oil on representative avian species as part of the Natural Resource Damage Assessment. The present report summarizes effects of oral exposure (n=26) of double-crested cormorants (DCCO; Phalacrocorax auritus) to 5 or 10ml oil kg day for up to 21 days or dermal application (n=25) of 13ml oil to breast and back feathers every three days totaling 6 applications in 21 days on organ weights and histopathology. Absolute and relative kidney and liver weights were increased in birds exposed to oil. Additionally, gross and/or histopathologic lesions occurred in the kidney, heart, pancreas and thyroid. Clinically significant renal lesions in the orally dosed birds included squamous metaplasia and increased epithelial hypertrophy of the collecting ducts and renal tubules and mineralization in comparison to controls. Gross cardiac lesions including thin walls and flaccid musculature were documented in both orally and dermally dosed birds and myocardial fibrosis was found in low numbers of dermally dosed birds only. Cytoplasmic vacuolation of the exocrine pancreas was noted in orally dosed birds only. Thyroid follicular hyperplasia was increased in dermally dosed birds only possibly due to increased metabolism required to compensate damaged feather integrity and thermoregulate. Gastrointestinal ulceration was found in orally dosed birds only. There were no significant hepatic histopathologic lesions induced by either exposure route. Therefore, hepatic histopathology is likely not a good representation of oil-induced damage. Taken together, the results suggest that oral or dermal exposure of DCCOs to artificially weathered MC252 crude oil induced organ damage that could potentially affect survivability.
During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnormalities, including softer, more distensible musculature, were noted upon gross necropsy in hearts from laughing gulls and double-crested cormorants exposed to weathered MC252 crude oil. A species specific, echocardiographic technique was developed for antemortem evaluation of function that was used to evaluate and better characterize cardiac dysfunction. Control (n=12) and treated (n=13) cormorant groups of similar sex-ratio and ages were dermally treated with approximately 13ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages. This resulted in a low to moderate external exposure. Upon visualization and clinical assessment of the hearts of all test subjects, comprehensive diagnostic cardiographic measurements were taken twice, prior to oil application and after a 21day dermal oil exposure. Oil-treated birds showed a decrease in cardiac systolic function, as characterized by an increased left ventricular internal dimension-systole and left ventricular stroke volume as well as concurrent decreased left ventricular ejection fraction and left ventricular fractional shortening when compared to both control birds' and the treated birds' time zero values. These changes are indicative of a possible dilative cardiomyopathy induced by oil exposure, although further elucidation of possible collagen damage is recommended. Arrhythmias including tachycardia in two treated birds and bradycardia in all treated birds were documented, indicating further clinically significant abnormalities induced by MC252 oil that warrant further investigation. A statistically significant increase in free calcium concentration, important to muscular and neurologic function in treated birds was also noted. This study documents that weathered MC252 oil caused clinically significant cardiac dysfunction that could result in mortality and decrease recruitment.
This study evaluates effects of feeding mercury (Hg) contaminated fish collected from streams on the Oak Ridge Reservation (ORR) on mink. Diets composed of 25, 50, or 75% fish collected from streams on the ORR were fed to mink beginning 3 months prior to breeding and ending 6 weeks following whelping. Mercury concentrations in diets, tissues of adult mink and their offspring, and physiological and reproductive effects were recorded and compared to concentrations and effects observed in mink fed diets composed of 75% fish collected from the Clinch River above the ORR or from the ocean. Mercury concentrations in prepared diets and in tissues of adult mink and their offspring increased progressively with increased percentage of ORR fish in the diets. Female mink fed diets containing 75% ORR fish had reduced body weight and a decreased number of kits compared to those fed diets containing 75% fish collected above the ORR or from the ocean. However, based on previously reported Hg concentrations associated with adverse effects in mink, the observed adverse effects are not thought to result from exposure to Hg.
Ovariectomized mink were fed diets containing zearalenone (ZEN) at concentrations of 0, 10 or 20 ppm with or without 0.5% hydrated sodium calcium aluminosilicate (HSCAS) for 24 days. Zearalenone at 10 and 20 ppm caused a significant increase in uterine weights, while 20 ppm ZEN resulted in significantly higher vulva swelling scores when compared to controls. The presence of HSCAS in the diet did not alter these hyperestrogenic effects of ZEN. In a second experiment, female mink were provided diets containing 20 ppm ZEN, 20 ppm ZEN plus 0.5% HSCAS or a control diet from 1 January 1989 through whelping (25 April to 15 May 1989). The females were given an opportunity to mate with untreated proven breeder males beginning on 1 March (day 59 of exposure). ZEN did not have an effect on the number of females whelping but there was a significant increase in gestation length, a decrease in litter size and an increase in kit mortality from birth to 3 weeks of age when compared to the control group and the group receiving the combination of ZEN and HSCAS. These results suggest that HSCAS can alleviate some of the reproductive effects of ZEN which are not related to its estrogenic action.
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