Waterdog, Gulf Coast


Necturus beyeri  


Adult length: 6-8.5 in.: color is an overall brown with lighter brown and black speckling; legs are short with four-toed feet; external gills look like feathery appendages on either side of their heads; tail is paddle-shaped and flattened. Sexually mature males can be distinguished by the swollen cloaca and pair of enlarged cloacal papillae that project posteriorly. Hatchlings are mottled with a few light spots dorsally. Older larvae generally resemble adults in shape and color pattern.  An abrupt metamorphosis does not occur.

Family

Proteidae

Order

Caudata

Class

Amphibia

Range

Louisiana, Mississippi, and Texas

Habitat

Clear, spring fed streams with sandy bottoms and an abundance of leaf beds

Life Expectancy

At least 6 – 7 years and perhaps to 20 years in captivity

Sexual Maturity

4 – 6 years

Diet

In the wild, they eat small aquatic invertebrates such as crayfish, isopods, amphipods, freshwater clams, and insects; in the Zoo, they are fed small fish, earthworms, and blackworms.

Status

IUCN – Least Concern

Behaviors

Gulf Coast waterdogs, as is true with all species of Necturus, are neotenic, retaining gills and an aquatic lifestyle through adulthood. They are found in sandy, spring-fed streams; they are not found in the turbid, sluggish waters characteristic of bayous, rivers, and lakes of the Lower Mississippi River System. Most adults are found in slow-moving sections of streams under large objects such as logs, flood debris, and other obstructions. Some Gulf Coast waterdogs live in stream bank burrows. Young juveniles inhabit bottom debris, especially leaf litter, where currents are slow and prey aggregate. Home range size is apparently relatively small. Adults are known to remain in the same stretch of stream for over 2.5 yr. Bart and Holzenthal (1985) suspect that Gulf Coast waterdogs aestivate in burrows during the summer and autumn, when invertebrate prey are scarce. Adults forage along logs, away from leaf-litter beds. Predators of the Gulf Coast waterdog are fish and other waterdogs.

Adaptions

Waterdogs never lose their gills during maturation from larvae. This aspect of their physiology is known as pedomorphosis. Despite having lungs, which appear to provide little use in respiration, waterdogs spend their entire lives underwater. The adult gills resemble fish gills in many ways, but differ from fish gills in that they are external and lack any form or operculum or covering. The bright red exposed gills are often found closed against the body in cool, highly oxygenated water. In warmer, poorly oxygenated water, the gills expand to increase water circulation and provide greater surface area for oxygen in-take. Waterdogs also absorb oxygen through their skin and by occasionally breathing air at the surface.

Special Interests

Necturus is a genus of aquatic salamander only found in the eastern United States. They are commonly known as Waterdogs and Mudpuppies. There has been significant controversy over the taxonomy of in the genus Necturus, particularly in regard to N. alabamensis (Alabama Waterdog), N. beyeri, and N. maculosus (Mudpuppy). However, electrophoretic evidence suggests N. beyeri is a distinct species. Gulf Coast waterdogs (Necturus beyeri) are thought to occur in two distinct regions: western populations are found in eastern Texas and west-central Louisiana; eastern populations are found in northern and western Mississippi. Supporting this interpretation, waterdogs from the major rivers draining into Mobile, Alabama (except for the Upper Black Warrior Drainage, which contains Black Warrior River waterdogs, Necturus alabamensis), are genetically indistinguishable from the eastern form of N. beyeri. Other names for the Gulf Coast waterdog are speckled waterdog and Beyer’s waterdog. The species name beyeri is in honor of George Eugene Beyer (1861-1926), “the pioneer student of Louisiana herpetology.” He was President of the LA Naturalists Society and a Member of the US Yellow Fever Institute and Commission to Veracruz, Mexico. He was a special inspector for the Biological Survey of the US Department of Agriculture.

Folklore

The name waterdog originates from the misconception that they make a dog-like barking sound.

Conservation

Petranka (1998) speculates that, similar to other river-dwelling fishes and amphibians, numbers of Gulf Coast waterdogs likely have been reduced due to siltation and pollution. The Gulf Coast waterdog is currently listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. Gulf coast waterdogs are not endangered or threatened, but the Jacksonville Zoo and Gardens has been working with this species to gain knowledge of this species’ habits and requirements. This will then lead to a better understanding of a similar species, the Alabama black warrior waterdog (Necturus alabamensis), which is endangered due to habitat loss and destruction.

Jacksonville Zoo History

The Jacksonville Zoo first received this species in 2008.

Exhibit

Amphibian Conservation Center