Factors affecting male-male competition in thirteen-lined ground squirrels

Intrasexual conflict and mating behavior were observed in a population of thirteen-lined ground squirrels ( Spermophilus tridecemlineatus ). Success in male-male competition was related strongly to male weight, whereas both the weight and age of males were correlated positively with estimated mating success.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46869/1/265_2004_Article_BF00295069.pd

Alarm calling behavior of the thirteen-lined ground squirrel, Spermophilus tridecemlineatus

Alarm calling in a population of thirteenlined ground squirrels, Spermophilus tridecemlineatus , was studied over a three-year period. Data on ground squirrel reactions to human and canine approaches and to the approach or presence of avian predators were used to quantify alarm calling behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46905/1/265_2004_Article_BF00299364.pd

Early Life Events Carry Over to Influence Pre-Migratory Condition in a Free-Living Songbird

Conditions experienced during development can have long-term consequences for individual success. In migratory songbirds, the proximate mechanisms linking early life events and survival are not well understood because tracking individuals across stages of the annual cycle can be extremely challenging. In this paper, we first use a 13 year dataset to demonstrate a positive relationship between 1st year survival and nestling mass in migratory Savannah sparrows (Passerculus sandwichensis). We also use a brood manipulation experiment to show that nestlings from smaller broods have higher mass in the nest relative to individuals from larger broods. Having established these relationships, we then use three years of field data involving multiple captures of individuals throughout the pre-migratory period and a multi-level path model to examine the hypothesis that conditions during development limit survival during migration by affecting an individual's ability to accumulate sufficient lean tissue and fat mass prior to migration. We found a positive relationship between fat mass during the pre-migratory period (Sept–Oct) and nestling mass and a negative indirect relationship between pre-migratory fat mass and fledging date. Our results provide the first evidence that conditions during development limit survival during migration through their effect on fat stores. These results are particularly important given recent evidence showing that body condition of songbirds at fledging is affected by climate change and anthropogenic changes to landscape structure

Data from: Partner switching can favor cooperation in a biological market

Intraspecific cooperation and interspecific mutualisms can be promoted by mechanisms that reduce the frequency with which cooperative organisms are exploited by unhelpful partners. One such mechanism consists of changing partners after interacting with an uncooperative individual. I used McNamara et al.'s (Nature, 451, 2008, 189) partner switching model as a framework to examine whether this mechanism can select for increased cooperative investment by house sparrows (Passer domesticus) collaborating to rear offspring; previous research on this species has shown that substantial cooperative investments by both pair members are required to achieve high pay-offs from collaborating. I found that the poorer the outcome of a breeding attempt relative to the number of eggs the female invested, the greater the likelihood of partner switching. The incidence of partner switching changed seasonally, with peak switching coinciding with an increase in the number of alternative partners available to females. After females switched partners, their breeding outcomes rose to match those of females that remained with the same partner; this was not the case for males that switched partners. Consistent with the model's prediction, males in stable partnerships achieved over 25% higher than average reproductive success, which was attributable to both persistently good breeding outcomes and their older partners' high fecundity. These results provide empirical support for the hypothesis that partner switching favours increased cooperative investment levels, and they demonstrate that variation in the relative value of by-product benefits can enhance that process

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An experimental test of the information model for negotiation of biparental care

Background: Theoretical modelling of biparental care suggests that it can be a stable strategy if parents partially compensate for changes in behaviour by their partners. In empirical studies, however, parents occasionally match rather than compensate for the actions of their partners. The recently proposed "information model'' adds to the earlier theory by factoring in information on brood value and/or need into parental decision-making. This leads to a variety of predicted parental responses following a change in partner work-rate depending on the information available to parents. Methodology/Principal Findings: We experimentally test predictions of the information model using a population of long-tailed tits. We show that parental information on brood need varies systematically through the nestling period and use this variation to predict parental responses to an experimental increase in partner work-rate via playback of extra chick begging calls. When parental information is relatively high, partial compensation is predicted, whereas when parental information is low, a matching response is predicted. Conclusions/Significance: We find that although some responses are consistent with predictions, parents match a change in their partner's work-rate more often than expected and we discuss possible explanations for our findings