Seasonal activity in dwarf waterdogs (Necturus punctatus) : risk management or resource acquisition?

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Daniel Scott Sollenberger (Creator)
Western Carolina University (WCU )
Web Site:
Joseph Pechmann

Abstract: Predators can have non-consumptive effects (NCE) on prey populations in addition to normal consumptive effects. One of these NCE may be changes in patterns of behavior to reduce predation risk. Aquatic salamanders of the genus Necturus exhibit seasonal activity patterns, with observations of Necturus peaking during mid-winter. Predator avoidance has been suggested as an explanation for cool season activity; however, another hypothesis is that increased Necturus activity during winter is related to increased prey availability in leaf packs. To test the willingness of juvenile dwarf waterdogs to forfeit a foraging opportunity in the presence of different predation threats, I constructed three aquatic raceways. Three juvenile Necturus along with live blackworms (Lumbriculus varigaetus) were added to one of two chambers in each raceway. After foraging behavior by all Necturus was observed, I added either a Rana clamitans tadpole (non-predator control), an adult Necturus (gape-limited conspecific predator), or a crayfish (non-gape-limited predator) to the first chamber in each raceway. I removed the barrier detaining the juvenile waterdogs and recorded the distance of each from the treatment chamber every two minutes for a total of 14 min. I also sampled Necturus and macroinvertebrates monthly from leaf packs in the South Fork of the Edisto River near Windsor, SC. The purpose of this field study was to examine the relationship between waterdog abundance in leaf packs and the abundance of macroinvertebrate prey as an alternative hypothesis for seasonal activity. Treatment had no effect on waterdog behavior during lab trials. Necturus density was positively correlated with macroinvertebrate density and maximum stream discharge rate during the previous 30 days in partial correlation analyses, as well as with a maximum previous discharge/macroinvertebrate abundance interaction. My results suggest dwarf waterdogs may not be abandoning foraging areas during summer to avoid predators. Instead, increase in discharge rate may act as a cue to stimulate waterdogs to leave their summer refugia and move into leaf packs when prey density is at its peak.

Additional Information

Language: English
Date: 2013
leaf pack, macroinvertebrates, Necturus, predation risk, risk sensitive foraging, waterdog
Necturus -- Behavior
Predation (Biology)

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