Meeting Abstract
One of the most challenging aspects of the marine environment for mammals is thermoregulation due to the high heat transfer rate of water. Despite this there are few marine mammal species found exclusively in tropical regions and little is known about the energetic consequences of warm water adaptations on locomotor costs in these species. Working with Hawaiian monk seals (Neomonachus schauinslandi) and West Indian manatees (Trichechus manatus) as our model tropical species, we used flow-through respirometry to measure resting metabolic rate (RMR), stroke cost (SC), and cost of transport (COT) in 2 adult manatees at Mote Marine Lab (Sarasota, FL) and 1 adult monk seal at Long Marine Lab (Santa Cruz, CA). We found low average RMRs for both the monk seal (748.7 kJ·hr-1) and manatees (885.9 kJ·hr-1) relative to other marine mammals. In contrast, SC and COT were in line with predicted marine mammal values for both the monk seal (SC = 5.1 J·kg-1·stroke-1, COT = 1.7 J·kg-1·m-1) and manatees (SC = 2.6 J·kg-1·stroke-1, COT = 1.0 J·kg-1·m-1). This dichotomy indicates that thermoregulatory costs strongly influence RMR, but that costs associated with locomotion are more strongly affected by hydrodynamic interactions. While allometric analyses have proven useful in predicting energetic costs for many marine mammal species, the divergent thermoregulatory and hydrodynamic factors highlighted here for tropical species need to be accounted for when modeling energetic costs across tropical, temperate, and polar species.
