Increased energy expenditure due to increased territorial defense in male lizards after phenotypic manipulation

Abstract

Fitness tradeoffs are difficult to examine because many fitness variables are correlated and vary in the same direction. Phenotypic manipulation circumvents many of these difficulties, and here we used this technique to examine mechanisms for tradeoffs between increased aggression (territorial defense) and survivorship. The behavioral phenotype of male mountain spiny lizards (Sceloporusjarrovi) was manipulated with testosterone to increase territorial defense, a sexually selected trait. We previously demonstrated that increased territorial defense results in a decrease in survival caused by a lower ratio of energy intake to energy expenditure. Here we measured energy consumption of increased territorial aggression using the doubly labeled water technique in the field and compared males with and without testosterone implants (Fig. 1). In a supplementary study we measured standard metabolic rate using captive lizards given similar testosterone implants to examine if an increase in energy expenditure was a result of only an increase in standard metabolic rate (Fig. 3). Our results indicated that a primary contribution to tradeoffs between increased territorial defense and survivorship could be made by a 31% increase in energy expenditure in the field that is not due to an increase in standard metabolic rate.

A unique life history among tetrapods: An annual chameleon living mostly as an egg

“…Hormones can control these trade-offs (42). For example, increased androgens in both natural populations and by experimental manipulation can be correlated with mating success (43,44) but are also known to contribute to traits typically associated with increased adult mortality rates (e.g., reduced survival, increased parasite loads, increased energetic expenditure) (45)(46)(47)(48)(49)(50). It seems possible that a change in the social structure in ancestral F. labordi, to a social system characterized by increased androgen levels or sensitivity, could contribute to increased intrinsic and/or extrinsic adult mortality.…”

Variation in Testosterone and Corticosterone in Amphibians and Reptiles: Relationships with Latitude, Elevation, and Breeding Season Length

“…Behaviors associated with malemale competition, such as mate attraction, mate guarding, and territorial aggression, are all energetically demanding (Sullivan and Walsberg 1985;Marler et al 1995;Emerson and Hess 2001;Husak et al 2007). Therefore, at high latitudes with increased male-male competition, males may have to sustain higher baseline corticosterone concentrations than males at lower latitudes.…”

Showing Red: Male Coloration Signals Same-Sex Rivals in an Australian Water Dragon

“…Decreased responses by males to a large model displaying exaggerated red coloration, relative to the same model when painted brown, further supports the hypothesis that display of red ventral coloration functions to signal rivals. One likely explanation of reduced responsiveness to the red model is that engagement with a larger intruder giving an aggressive signal (Baird et al, 2012) would carry high costs (Marler and Moore, 1988;Marler et al, 1995).…”