Don't get between a salamander and her eggs. The concept usually applies to a mother bear and her cubs, but it rings true for this small amphibian as well -- particularly as the eggs get closer to hatching. A study has found that female salamanders grow more aggressive in defending their nests as their eggs mature. Other factors, including the size of the mother, were insignificant.
An article in the December 2010 issue of the journal Herpetologica describes the behavior of the eastern red-backed salamander, found in forests of North America. The females proved to be more vigorous about guarding clutches of eggs than territory or food.
The study was conducted in a laboratory setting, using wild salamanders caught in New Hampshire. Female salamanders and their nests of eggs were "threatened" by the introduction of a nonbrooding female salamander for 15-minute intervals.
While the first reaction of many mothers was to curl tightly around their eggs to protect them, substantially more aggressive behavior toward the intruder followed. In many instances, nudging, chasing, and snapping behaviors eventually gave way to repeatedly biting the intruder.
The female red-backed salamander may reproduce only every two years because of the substantial energy required to produce and attend her clutch. As the eggs become more viable, the mother's protection increases. The research found that mothers were more aggressive in defending their six-week old eggs than their four-week old eggs.
At the same time, the number of eggs in the nest and the size of the mother did not appear to make a difference in her aggression. These salamanders have the ability to recognize the developmental stage of their eggs, or at least are able to determine the amount of time that has passed since they laid their eggs. The older the brood, the more likely it is to survive to hatching, making it more important to the mother.
- Jan K. Tornick. Factors Affecting Aggression During Nest Guarding in the Eastern Red-Backed Salamander (Plethodon Cinereus). Herpetologica, Volume 66, Issue 4, December 2010
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