Wildlife Conservation: Breeding Eastern Tiger Salamanders

Amphibian breeding season is here! That means it’s time to start helping amphibians get in the mood for love and romance.

The Institution of Museum and Library Sciences (IMLS) recently awarded a $500,000 National Leadership Grant for the purpose of improving reproduction within captive assurance colonies of imperiled salamanders. The Detroit Zoological Society is one of the primary partners on this grant. My doctoral research focused on salamanders, their reproductive physiology and techniques to help them breed, and that very research was the basis for the recent IMLS grant proposal.

Other partners on the grant include Mississippi State University and Omaha’s Henry Doorly Zoo and Aquarium. Now that the grant was awarded, techniques must be taught to the other partners so we can all work together in salamander conservation efforts. I recently visited Mississippi State University in order to train the other principal investigators and the graduate students involved on this salamander grant in principles of natural salamander reproduction and performing assisted reproduction techniques with salamanders.

The training session involved eastern tiger salamanders (Ambystoma tigrinum), which are regionally threatened and endangered in various areas of North America. Like many species of salamanders, the tiger salamander is very difficult to breed in human care. Similar to other species in the “mole salamander” family, tiger salamanders respond to changes in air pressure and temperature when seasonal rain storms occur. These storms are what cue breeding behavior and are very difficult to replicate in human care. Without the ability to provide the appropriate “mood”, tiger salamanders in human care will not often feel romantically inclined. Natural breeding is always the first goal when breeding animals for conservation, but sometimes this is extremely challenging. In these cases, we use alternative techniques while we perfect replicating the natural breeding environment.

In vitro fertilization is a technique used to assist salamanders and other amphibians in breeding. Most salamander species undergo internal fertilization, in which the female picks up a capsule of male sperm, called a spermatophore, which the male has deposited into the environment. The female holds the sperm in an internal pouch that she later empties over her eggs as the eggs are laid. In in vitro fertilization of salamanders, sperm is collected from males by giving them a massage. Eggs are then collected from the female into a small dish where sperm is placed on top of the eggs. Just add water, and presto, you have salamander babies. Of course, it is never just that easy, but the concept is straightforward.

I trained the other primary investigators and students in other techniques as well, including cryopreservation – or freezing and long-term storage – of salamander sperm and sperm quality assessment. The training was very successful, with nearly 100 tiger salamander babies produced. Now the trainees can go on to teach more amphibian conservationists, and we can save more species by assisting with breeding!

– Dr. Ruth Marcec is the director of the National Amphibian Conservation Center at the Detroit Zoo.

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