Document: CRA-3-49-1

The effect of feeding frequency on growth: Has the physiology of intermittent feeders co-evolved with an infrequent feeding strategy?

WILMHOFF, C.D.* and W.H.N.GUTZKE

The University of Memphis, Memphis, TN 38152, USA ¹

Abstract:
An organism's rate of growth affects its survival, reproduction, and ultimate fitness. Thus it is not surprising a vast amount of information is available concerning the factors (e.g. temperature, maintenance costs, and diet quality and quantity) affecting growth. The effect of feeding frequency on growth, however, has remained relatively uninvestigated. Feeding frequency has been associated with foraging mode: ambush (sit-and-wait) predators feed less frequently than actively foraging species. It has been proposed that intermittent feeding frequencies exhibited by ambush predators have co-evolved with the digestive physiology of these organisms. Specifically ambush predators that feed frequently will incur higher costs associated with digestion (e.g. specific dynamic action). According to this proposal intermittent feeders should exhibit decreased growth rates if feeding frequency increases while total caloric intake remains unchanged. The present study tested the aforementioned hypothesis by investigating the effects of feeding frequency and total caloric intake on growth in an intermittent feeder, the timber rattlesnake (Crotalus horridus). A counterbalanced repeated measures design was used in which snakes were fed house mice (Mus musculus) according to either a weekly or monthly feeding frequency during two consecutive years. In 1998, animals were fed ad libitum during feeding trials (allowing total caloric intake to vary) whereas in 1999, animals were fed a total of 4 mice per month equaling approximately 20% of their body mass. Feeding frequency and the total mass of mice consumed demonstrated significant effects on the overall change in snake body mass during both years. Snakes exhibited higher growth rates during weekly feeding trials in both years calling into question the hypothesis that the physiology of intermittent feeders is adapted to an infrequent feeding frequency. The change in body mass per gram of mouse consumed was affected by feeding frequency in 1999 indicating that feeding frequency may be affecting growth by affecting digestive and/or assimilation efficiencies.

Keywords: Feeding Frequency, Growth, Digestive Efficiency, Foraging Mode, Viperidae

This abstract is being presented at: 1:30 PM in session:
Oral Session #63: Evolutionary Ecology.