Captivity, reintroduction, and the boreal toad microbiome. Boreal toad microbiome

As captive assurance populations and reintroduction programs increase, a better understanding of how microbial symbionts respond during animal translocations is critical. We examined changes in microbes associated with boreal toads (Anaxyrus boreas boreas), a threatened amphibian, after reintroduction to the wild following captive rearing. Previous studies demonstrate that developmental life stage is an important factor in their microbiomes. We collected 16S marker-gene sequencing datasets to investigate: i) comparisons of the skin, mouth, and gut bacteria of boreal toads across four developmental life stages in captivity and the wild, ii) tadpole skin bacteria before and after reintroduction to the wild, and iii) adult skin bacteria during reintroduction to the wild. We demonstrated that differences occur across the skin, gut, and mouth microbial communities in captive versus wild boreal toads, and that the degree of difference depends on developmental stage. Skin bacterial communities from captive tadpoles were more similar to their wild counterparts than captive post-metamorphic individuals were to their wild counterparts. When captive reared tadpoles were introduced to a wild site, their skin bacteria changed to mirror wild tadpoles within weeks. Similarly, the microbiome of reintroduced adult boreal toads also shifted to mirror that of wild-type toads. Our results indicate that the microbial signature of captivity does not persist after release into natural habitat. The relationship between changing microbes and host health is not well understood for the majority of animal species but is an important part of wildlife conservation.