Maternal Care and Learned Foraging in Bottlenose Dolphins (Tursiops truncates) Janalee Martin
Behavioral Ecology Fall 2012
Maternal care is a major factor in juvenile development and studies dating back several decades have shown the impact of early life events on the development of behavioral responses to differences in maternal care (Francis and Meaney, 1999). Maternal separation causes acute stress in individuals resulting in them being extremely fearful in situations that they have never been in before. Animals tend to be more timid when exploring or feeding in new environments as well as exhibiting stronger reactions to loud noises (Meaney, 2001). These periods of stress cause individuals to focus their entire attention on the unfamiliar surroundings, instead of the particular task that they are trying to accomplish (Francis and Meaney, 1999). Individuals using their energy on making sure their surroundings are safe should be using it on key survival factors, like foraging.
The knowledge of how to forage efficiently must be passed down to juvenile individuals so that they can develop the techniques that will ensure their survival. Knowing which foraging strategies and prey types that will provide them with a maximum energy gain is directly related to optimum foraging. The optimal foraging theory states that individuals optimize a currency and identify the decision rule that maximizes that currency while laboring under energy and time constraints. Along with that, the marginal value theorem suggests that there is a specific time that an individual should stop foraging in that specific food patch as the amount of energy gain begins to decrease the more the resources in the patch are exploited. These principles allow individuals to develop foraging strategies that will benefit them the most.
Bottlenose dolphins (Tursiops truncates) have several strategies that they employ to help them forage successfully and ensure their survival. Tactics include beach stranding, tool use, and slapping the water with their flukes to stun, kill, or scare up prey (Mann and Sargeant, 2003). Juvenile dolphins must learn the most efficient hunting techniques, prey type, and optimal foraging time to survive to and through adulthood. The ability to forage effectively in bottlenose dolphins is believed to be passed down through observation and mimicry (Kuczaj and Yeater, 2010) to individuals through each generation. The choice of which behaviors to use in a foraging sequence can be influenced by a variety of factors (Nowacek, 2002). This includes matrilineal transmission and social learning, which is thought to help juveniles to quickly adjust to their habitat (Mann and Sargeant, 2009) as well as how to know when too much energy is being expended compared to how much energy is being gained. The foraging behavior of young dolphins is believed to be facilitated by their mothers (Mann and Sargeant, 2003) and that imitation comes early in life through these mother-calf interactions (Bauer et al. 2006). METHODS
The objective of my experiment is to determine how foraging behaviors and techniques of bottlenose dolphins are learned by calves. Is foraging behavior passed down vertically (from mother to calf), through social learning (observation), or both? I hypothesize that juvenile dolphins acquire their foraging knowledge through both their mothers and social learning. My study will be a long term one (at least 10 years) focusing on female bottlenose dolphins and their offspring in Monterey Bay, Ca. Such a length of time will allow me to track the calves to adulthood and beyond so that I can see if their foraging and hunting tactics are similar to those of their mother’s, rather than to other females in the population. I will be observing a variety of foraging behaviors in overlapping foraging habitats. This will help ensure that the calves’ diet is more related to their mothers’ due to transmission of...
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