The management of energy use is critically important in the lives of animals, and consequently understanding how energy is used when animals walk is a major goal in evolutionary biology. Although many animals have been shown to achieve high levels of energetic efficiency while walking and running by using energy saving mechanisms, it is possible that in some situations other needs prevent animals from saving energy. For example, the need to maintain stability while walking on branches or the need to approach a prey item without being detected may have greater survival consequences than increased energy use.
A comparison of walking energetics between members of the dog and cat families provides an ideal opportunity to investigate some of these performance tradeoffs in detail. Previous research has revealed that domestic cats walk inefficiently compared to domestic dogs and that footfall patterns that promote stability contribute to this poor energy recovery. In contrast, dogs have been found to be highly energetically efficient while walking. These differences may be associated with differences in hunting strategy or simply body size. By using a combination of force plate measurements, motion analysis, and measurements of oxygen uptake on dogs of different sizes, this project will begin to dissect the effects of hunting style and body size on the energetics of walking.
Florida International University is an urban, Latino majority research institution with a high proportion of first-generation college students. Opportunities will be made available for women, minorities and other underrepresented groups as undergraduate research assistants, graduate students, and postdoctoral researchers.
The ways in which energy is used as an animal moves about its environment can be extremely important in the life of that animal and to the evolution of the species. Small energy savings can add up to big payoffs if the animal moves around a great deal, but may not be that important if the animal does not travel much. It has long been known that some animals are able to save energy while walking by recycling energy from one form to another, much as a pendulum uses height to create motion, then uses that motion to rise back to the original height. Previous studies have shown that dogs are very good at recycling energy in this way, but I found in prior work that domestic cats are not nearly as good at it. There are at least two possible reasons for this difference. One is that cats are simply smaller than the large dogs that were studied and that small animals are not able to use this method to save energy. The second has to do with their hunting strategies. Cats are sit and wait predators who stealthily stalk their prey over short distances, then use a quick burst of speed to overtake them. Dogs, on the other hand, are pursuit predators who will chase prey to exhaustion over long distances. It is possible that because dogs travel long distances, saving this energy is very important to them, but cats may have other priorities that outweigh the benefits of the energy savings. My research program is designed to distinguish between these two possibilities. This year-long research starter award provided funds to purchase equipment to get this project off the ground as I begin my career as an independent biologist. I have used the money to purchase a treadmill and video equipment and I have begun to collect preliminary data from dogs while walking on the treadmill. This equipment will allow me to compare the movements of large and small dogs to measure whether small dogs move more like large dogs or like cats. This will help answer the question about whether size accounts for the differences seen in energy recovery between dogs and cats. I have also used the funds to purchase equipment that will allow me to measure the actual energy expenditure associated with walking in dogs and cats of different sizes. If the differences in body movements, mechanical energy exchange, and metabolic cost are more different between large and small dogs than between dogs and cats, we can conclude that the differences are an effect of body size. If the differences are greater between dogs and cats regardless of body size, then these differences may be the result of adaptation to different hunting strategies or habitat use patterns.
