The effects of increased hay-to-grain ratio on behavior, metabolic health measures, and fecal bacterial communities in four Masai giraffe (Giraffa camelopardalis tippelskirchi) at Cleveland Metroparks Zoo.

We evaluated whether increasing the hay-to-grain ratio offered to Masai giraffe (Giraffa camelopardalis tippelskirchi) at Cleveland Metroparks Zoo would reduce oral stereotypies and alter feeding behaviors, maintain or increase serum calcium-to-phosphorus ratio, decrease serum insulin-to-glucose ratio and salivary insulin, and alter fecal bacterial community structure. Giraffe transitioned to a ∼90:10 hay-to-grain ratio in even increments over 8 weeks. A ration balancer was added during the seventh week of transition to ensure proper mineral and nutrient balance. We collected (1) behavioral data collected approximately daily using instantaneous focal sampling; (2) serum collections every other week for insulin-to-glucose and calcium-to-phosphorus ratio analysis and saliva weekly for insulin analysis; and (3) weekly fecal sample collections to examine changes in bacterial community structure during the 8 weeks preceding and following the diet change. After the diet change, giraffe spent significantly more time feeding and less time performing tongue and mouth stereotypies, people-directed and alert behaviors. Salivary and serum insulin and serum insulin-to-glucose ratio decreased, and fecal bacterial community structure changed significantly. However, serum calcium-to-phosphorus ratio remained >1:1 throughout the study. While further studies are needed to elucidate the nature and implications of the change in fecal bacterial community structure and metabolic hormones, the results of this study show promise for incremental improvements in health and welfare from feeding a higher proportion of forage in the diet.

Gut microbiome composition is associated with cardiac disease in zoo-housed western lowland gorillas (Gorilla gorilla gorilla).

Cardiac disease is a leading cause of mortality in zoo-housed western lowland gorillas (Gorilla gorilla gorilla). The gut microbiome is associated with cardiac disease in humans and similarly the gut microbiome may be associated with cardiac diseases in close relatives of humans, such as gorillas. We assessed the relationship between cardiac disease and gut bacterial composition in eight zoo-housed male western lowland gorillas (N = 4 with and N = 4 without cardiac disease) utilizing 16S rRNA gene analysis on the Illumina MiSeq sequencing platform. We found bacterial composition differences between gorillas with and without cardiac disease. Bacterial operational taxonomic units from phyla Bacteroidetes, Spirochaetes, Proteobacteria and Firmicutes were significant indicators of cardiac disease. Our results suggest that further investigations between diet and cardiac disease could improve the management and health of zoo-housed populations of this endangered species.

Legacy of road salt: Apparent positive larval effects counteracted by negative postmetamorphic effects in wood frogs.

Road salt runoff has potentially large effects on wetland communities, but is typically investigated in short-term laboratory trials. The authors investigated effects of road salt contamination on wood frogs (Rana sylvatica) by combining a field survey with 2 separate experiments. The field survey tested whether wood frog larval traits were associated with road salt contamination in natural wetlands. As conductivity increased, wood frog larvae were less abundant, but those found were larger. In the first experiment of the present study, the authors raised larvae in outdoor artificial ponds under 4 salt concentrations and measured larval vital rates, algal biomass, and zooplankton abundance. Salt significantly increased larval growth, algal biomass, and decreased zooplankton abundance. In the second experiment, the authors raised larvae to metamorphosis in the presence and absence of salt contamination and followed resulting juvenile frogs in terrestrial pens at high and low densities. Exposure to road salt as larvae caused juvenile frogs to have greater mortality in low-density terrestrial environments, possibly because of altered energy allocation, changes in behavior, or reduced immune defenses. The present study suggests that low concentrations of road salt can have positive effects on larval growth yet negative effects on juvenile survival. These results emphasize the importance of testing for effects of contaminants acting through food webs and across multiple life stages as well as the potential for population-level consequences in natural environments.

Larval Environment Alters Amphibian Immune Defenses Differentially across Life Stages and Populations.

Recent global declines, extirpations and extinctions of wildlife caused by newly emergent diseases highlight the need to improve our knowledge of common environmental factors that affect the strength of immune defense traits. To achieve this goal, we examined the influence of acidification and shading of the larval environment on amphibian skin-associated innate immune defense traits, pre and post-metamorphosis, across two populations of American Bullfrogs (Rana catesbeiana), a species known for its wide-ranging environmental tolerance and introduced global distribution. We assessed treatment effects on 1) skin-associated microbial communities and 2) post-metamorphic antimicrobial peptide (AMP) production and 3) AMP bioactivity against the fungal pathogen Batrachochytrium dendrobatidis (Bd). While habitat acidification did not affect survival, time to metamorphosis or juvenile mass, we found that a change in average pH from 7 to 6 caused a significant shift in the larval skin microbial community, an effect which disappeared after metamorphosis. Additionally, we found shifts in skin-associated microbial communities across life stages suggesting they are affected by the physiological or ecological changes associated with amphibian metamorphosis. Moreover, we found that post-metamorphic AMP production and bioactivity were significantly affected by the interactions between pH and shade treatments and interactive effects differed across populations. In contrast, there were no significant interactions between treatments on post-metamorphic microbial community structure suggesting that variation in AMPs did not affect microbial community structure within our study. Our findings indicate that commonly encountered variation in the larval environment (i.e. pond pH and degree of shading) can have both immediate and long-term effects on the amphibian innate immune defense traits. Our work suggests that the susceptibility of amphibians to emerging diseases could be related to variability in the larval environment and calls for research into the relative influence of potentially less benign anthropogenic environmental changes on innate immune defense traits.