Telencephalic lesions and behavior in the teleost, macropodus opercularis: Reproduction, startle reaction, and operant behavior in the male

Bilateral ablation of the telecephalon at the level of the anterior commissure blocked reproduction in male paradise fish. Lesioned males performed species typical displays at the start of the spawning trial but thereafter avoided the female, and they did not build nests. All the sham-operated males spawned and built nests. The reaction of the male to a startle stimulus and the rate of operant responding for visual reinforcement were used as additional, independent measures of the behavioral effects of the ablation. Removal of the telencephalon greatly increased startle reactivity and decreased the rate of operant responding. Hyperreactivity could account for long response latencies, reduced mobility, and other reported effects of telencephalic ablation in teleosts which have previously been attributed to impaired nonspecific arousal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21665/1/0000052.pd

Telencephalic lesions and behavior in the teleost, Macropodus opercularis: Further analysis of reproductive and operant behavior in the male

Ablation of the telencephalic hemispheres blocked reproductive behavior and decreased the rate of operant responding for conspecific visual reinforcement. Repeated administration of operant conditioning sessions for 4 weeks following the ablation resulted in a partial recovery of the operant rate but not of reproductive behavior. Social isolation, which increases reactivity in Macropodus, had no significant effect on the operant rate in sham-operated or lesioned males. Lesioning resulted in a significant reduction of testes weight and the gonadosomatic index in 8 weeks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21667/1/0000054.pd

Flexibility but no coordination of visits in provisioning riflemen

Parental care strategies occupy a continuum from fixed investments that are consistent across contexts to flexible behaviour that largely depends on external social and environmental cues. Determining the flexibility of care behaviour is important, as it influences the outcome of investment games between multiple individuals caring for the same brood. We investigated the repeatability of provisioning behaviour and the potential for turn taking among breeders and helpers in a cooperatively breeding bird, the rifleman, Acanthisitta chloris. First, we examined whether nest visit rate is an accurate measure of investment by assessing whether carers consistently bring the same size of food, and whether food size is related to nest visit rate. Our results support the use of visit rate as a valid indicator of parental investment. Next, we calculated the repeatability of visit rate and food size to determine whether these behaviours are fixed individual traits or flexible responses to particular contexts. We found that riflemen were flexible in visit rate, supporting responsive models of care over ‘sealed bids’. Finally, we used runs tests to assess whether individual riflemen alternated visits with other carers, indicative of turn taking. We found little evidence of any such coordination of parental provisioning. We conclude that individual flexibility in parental care appears to arise through factors such as breeding status and brood demand, rather than as a real-time response to social partners

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

Selfish or altruistic? An analysis of alarm call function in wild capuchin monkeys, Cebus apella nigritus

Alarm calls facilitate some antipredatory benefits of group living but may endanger the caller by attracting the predator's attention. A number of hypotheses invoking kin selection and individual selection have been proposed to explain how such behaviour could evolve. This study tests eight hypotheses for alarm call evolution by examining the responses of tufted capuchin monkeys to models of felids, perched raptors and vipers. Specifically, this study examines: (1) differences between individuals in their propensity to call in response to different threat types, (2) whether there is an audience effect for alarm calling and (3) the response of conspecifics to alarms. Results indicate that the benefits likely to be afforded to the caller vary with stimulus type. Alarm calling in response to felids is most likely selfish, with calls apparently directed towards both the predator and potential conspecific mobbers. Alarm calling in response to vipers attracts additional mobbers as well, but also appears to be driven by kin selection in the case of males and parental care benefits in the case of females. Alarm responses to perched raptors are rare, but seem to be selfish, with callers benefiting by recruiting additional mobbers

It takes two: Evidence for reduced sexual conflict over parental care in a biparental canid

In biparental systems, sexual conflict over parental investment predicts that the parent providing care experiences greater reproductive costs. This inequality in parental contribution is reduced when offspring survival is dependent on biparental care. However, this idea has received little empirical attention. Here, we determined whether mothers and fathers differed in their contribution to care in a captive population of coyotes (Canis latrans). We performed parental care assays on 8 (n = 8 males, 8 females) mated pairs repeatedly over a 10-week period (i.e., 5–15 weeks of litter age) when pairs were first-time breeders (2011), and again as experienced breeders (2013). We quantified consistent individual variation (i.e., repeatability) in 8 care behaviors and examined within- and among-individual correlations to determine if behavioral plasticity within or parental personality across seasons varied by sex. Finally, we extracted hormone metabolites (i.e., cortisol and testosterone) from fecal samples collected during gestation to describe potential links between hormonal mechanisms and individual consistency in parental behaviors. Parents differed in which behaviors were repeatable: mothers demonstrated consistency in provisioning and pup-directed aggression, whereas fathers were consistent in pup checks. However, positive within-individual correlations for identical behaviors (e.g., maternal versus paternal play) suggested that the rate of change in all behaviors except provisioning was highly correlated between the sexes. Moreover, positive among-individual correlations among 50% of identical behaviors suggested that personality differences across parents were highly correlated. Lastly, negative among-individual correlations among pup-directed aggression, provisioning, and gestational testosterone in both sexes demonstrated potential links between preparental hormones and labile parental traits. We provide novel evidence that paternal contribution in a biparental species reaches near equivalent rates of their partners

The Perfect Family: Decision Making in Biparental Care

Background Previous theoretical work on parental decisions in biparental care has emphasized the role of the conflict between evolutionary interests of parents in these decisions. A prominent prediction from this work is that parents should compensate for decreases in each other\u27s effort, but only partially so. However, experimental tests that manipulate parents and measure their responses fail to confirm this prediction. At the same time, the process of parental decision making has remained unexplored theoretically. We develop a model to address the discrepancy between experiments and the theoretical prediction, and explore how assuming different decision making processes changes the prediction from the theory. Model Description We assume that parents make decisions in behavioral time. They have a fixed time budget, and allocate it between two parental tasks: provisioning the offspring and defending the nest. The proximate determinant of the allocation decisions are parents\u27 behavioral objectives. We assume both parents aim to maximize the offspring production from the nest. Experimental manipulations change the shape of the nest production function. We consider two different scenarios for how parents make decisions: one where parents communicate with each other and act together (the perfect family), and one where they do not communicate, and act independently (the almost perfect family). Conclusions/Significance The perfect family model is able to generate all the types of responses seen in experimental studies. The kind of response predicted depends on the nest production function, i.e. how parents\u27 allocations affect offspring production, and the type of experimental manipulation. In particular, we find that complementarity of parents\u27 allocations promotes matching responses. In contrast, the relative responses do not depend on the type of manipulation in the almost perfect family model. These results highlight the importance of the interaction between nest production function and how parents make decisions, factors that have largely been overlooked in previous models

Joint care can outweigh costs of nonkin competition in communal breeders

Competition between offspring can greatly influence offspring fitness and parental investment decisions, especially in communal breeders where unrelated competitors have less incentive to concede resources. Given the potential for escalated conflict, it remains unclear what mechanisms facilitate the evolution of communal breeding among unrelated females. Resolving this question requires simultaneous consideration of offspring in noncommunal and communal nurseries, but such comparisons are missing. In the Seychelles warbler Acrocephalus sechellensis, we compare nestling pairs from communal nests (2 mothers) and noncommunal nests (1 mother) with singleton nestlings. Our results indicate that increased provisioning rate can act as a mechanism to mitigate the costs of offspring rivalry among nonkin. Increased provisioning in communal broods, as a consequence of having 2 female parents, mitigates any elevated costs of offspring rivalry among nonkin: per-capita provisioning and survival was equal in communal broods and singletons, but lower in noncommunal broods. Individual offspring costs were also more divergent in noncommunal broods, likely because resource limitation exacerbates differences in competitive ability between nestlings. It is typically assumed that offspring rivalry among nonkin will be more costly because offspring are not driven by kin selection to concede resources to their competitors. Our findings are correlational and require further corroboration, but may help explain the evolutionary maintenance of communal breeding by providing a mechanism by which communal breeders can avoid these costs

Transgenerational plasticity and selection shape the adaptive potential of sticklebacks to salinity change

In marine climate change research, salinity shifts have been widely overlooked. While widespread desalination effects are expected in higher latitudes, salinity is predicted to increase closer to the equator. Here, we use the steep salinity gradient of the Baltic Sea as a space‐for time design to address effects of salinity change on populations. Additionally, genetic diversity, a prerequisite for adaptive responses, is reduced in Baltic compared to Atlantic populations. On the one hand, adaptive transgenerational plasticity (TGP) might buffer the effects of environmental change, which may be of particular importance under reduced genetic variation. On the other hand, physiological trade‐offs due to environmental stress may hamper parental provisioning to offspring thereby intensifying the impact of climate change across generations (non‐adaptive TGP). Here, we studied both hypothesis of adaptive and non‐adaptive TGP in the three‐spined stickleback (Gasterosteus aculeatus) fish model along the strong salinity gradient of the Baltic Sea in a space‐for‐time experiment. Each population tolerated desalination well, which was not altered by parental exposure to low salinity. Despite a common marine ancestor, populations locally adapted to low salinity lost their ability to cope with fully marine conditions, resulting in lower survival and reduced relative fitness. Negative transgenerational effects were evident in early life stages, but disappeared after selection via mortality occurred during the first 12‐30 days post hatch. Modeling various strengths of selection, we showed that non‐adaptive transgenerational plasticity accelerated evolution by increasing directional selection within the offspring generation. Qualitatively, when genetic diversity is large, we predict that such effects will facilitate rapid adaptation and population persistence, while below a certain threshold populations suffer a higher risk of local extinction. Overall, our results suggest that transgenerational plasticity and selection are not independent of each other and thereby highlight a current gap in TGP studies