Marler Lab

Behavioral Neuroendocrinology of Social Behavior

The Marler Lab is interested in understanding the relationship between social behavior and the environment, particularly the physiological mechanisms that link variation in the social environment to specific changes in behavior. This includes how changes in hormone levels influence social behaviors, as well as how social interactions feed back on behavior and neuroendocrinology, causing plasticity in behavior and its physiological underpinnings. We employ a variety of vertebrate model systems, each of which permits detailed analysis of interactions among behavior, the environment, and neuroendocrine systems. For example, different species of Peromyscus mice have different mating systems and display different levels of aggression and paternal behavior. Peromyscus mice are ideal for manipulations of the social environment during development. Gray treefrogs, Hyla versicolor, are ideal for field studies examining how hormone manipulations influence behavior both in the manipulated individual and individuals in their natural social environment. Questions we have recently been addressing include the following:

See the our people page to view the research and contact information for current and former lab members.

The Social Environment and Development

What is the impact of the social environment during development on future adult behavior and what physiological and neural mechanisms are involved in this process?  What specific behavioral traits of the parents influence adult behavior of unrelated offspring and do maternal and paternal effects differ? These questions allow us to ask how behavioral traits can be transmitted through generations through nongenetic mechanisms.

Arginine Vasopressin -- Aggression and Paternal Behavior

We have found that levels of arginine vasopressin (AVP), a neuropeptide hormone associated with aggression, are influenced by the social environment during development. Does variation in paternal care cause changes in the AVP levels of a male's offspring? Does the effect of AVP on aggression differ depending on a species' mating system and type of aggression?  How does a single aggressive encounter influence levels of arginine vasopressin immunoreactivity?

The Winner Effect

Is there a winner effect (a phenomena in which winning an encounter increases the probability of winning future encounters) in the monogamous Peromyscus californicus?  Does this social experience influence future male behavior in encounters?  Is there a ‘challenge effect’ (a transient increase in testosterone after an aggressive encounter) in rodents? Does the winner effect and associated hormonal changes differ between species with different mating systems and levels of territoriality?

Challenge Effects and Winner Effects

Is the winner effect in males mediated through the challenge effect, that is, through changes in testosterone or other steroid hormones?  What brain areas are involved in the winner effect? How does winning multiple encounters influence gene activation? We want to identify not only behavioral plasticity, but also the plasticity that can occur in the endocrine and neural bases that underlie these behaviors.

Neuroendocrine Basis of Female Aggression (Progesterone and Arginine Vasopressin)

The challenge effect occurs in males across a wide variety of species.  Does this also occur in females?  The female hormonal milieu across the estrus cycle is very complex.  Do the hormones that change across the estrus cycle also change in response to social stimuli such as an aggressive encounter with a conspecific female?  How do these hormones influence aggression? These questions are important because the hormonal and neural mechanisms underlying nonmaternal female aggression and, in particular, the plasticity in behavior and mechanisms are not well understood.

Effects of Testosterone and Aromatase on Social Behavior

 Does testosterone always decrease paternal behavior, or can testosterone increase paternal behavior via mechanisms that are similar to maternal behavior (i.e. aromatization of testosterone to estrogen)?  Hormones can be important in linking a suite of behavioral traits, including increasing some behaviors while decreasing others.  The role of hormones in tradeoffs between different behavioral traits may, however, differ significantly among species depending on life history traits.

Arginine Vasotocin and Acoustic Communication in Treefrogs and Tungara frogs

How do neurohormones, such as arginine vasotocin, influence acoustic communication and how do the behavioral changes evoked through hormonal changes influence other individuals in the natural environment?  Does arginine vasotocin simply increase calling behavior in frogs or are specific call characteristics changed and is the hormonal effect still influenced by the social environment?  These questions are important because we need to understand whether hormones/neurochemicals are simply modifying behavior at a very general level or whether these effects are both more specific and modifiable by the social environment.

Antipredator Behavior and Aggression Tradeoff

Tradeoffs occur among a variety of behaviors.  One tradeoff that has been understudied is the potential one between aggression and antipredator behavior. Are these behaviors linked and does testosterone decrease antipredator behavior while increasing aggressive behavior in a species that is territorial throughout the year?
 

Effects of Testosterone on Parasite Load

The evolution of behavior/hormonal interactions can be studied by manipulating hormonal levels and examining the costs and benefits of the behavioral and physiological changes.  Increased testosterone now has been linked to a decrease in survivorship in a variety of species, including the lizard Sceloporus jarrovi.  The mechanisms through which testosterone decreases survivorship are still being identified.  For example, the effect of testosterone on the immune system might occur because of direct effects of on the immune system or indirectly through behavioral changes.  We have identified a negative correlation between testosterone levels and number of ectoparasites in the S. jarrovi.

Research supported by the National Science Foundation Grant (Catherine Marler), National Research Service Awards (Ellen Davis), National Institutes of Mental Health Predoctoral Fellowships (Janet Bester-Meredith and Brian Trainor), and the Ford Foundation (Temitayo Oyegbile).

Page created by Nicole Kime, with material from Brian Trainor. 

Last updated 12 September, 2003.
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