Body shape changes associated with reproductive status, nutritive condition and growth in right whales Eubalaena glacialis and E. australis

Abstract

Mammalian reproduction is metabolically regulated; therefore, the endangered status and high variability in reproduction of North Atlantic right whales Eubalaena glacialis necessitate accurate assessments at sea of the nutritional condition of living individuals. Aerial photogrammetry was used to measure dorsal body width at multiple locations along the bodies of free-swimming right whales at different stages of the female reproductive cycle (E. glacialis) and during the initial months of lactation (mother and calf Eubalaena australis) to quantify changes in nutritional condition during energetically demanding events. Principal components analyses indicated that body width was most variable at 60% of the body length from the snout. Thoracic, abdominal and caudal body width of E. australis thinned significantly during the initial months of lactation, especially at 60% of body length from the snout, while their calves' widths and widthto-length ratios increased. The body shape of E. glacialis that had been lactating for 8 mo was significantly thinner than non-lactating, non-pregnant E. glacialis. Body shape of E. glacialis measured in the eighth month of lactation was significantly thinner than that of E. australis in the first month, but did not differ from that of E. australis in the third and fourth months. Body width was comparable with diameter calculated from girth of carcasses. These results indicate that mother right whales rely on endogenous nutrient reserves to support the considerable energy expenditure during the initial months of lactation; therefore, photogrammetric measurements of body width, particularly at 60% of body length from the snout, are an effective way to quantitatively and remotely assess nutritional condition of living right whales.

A small unmanned aerial system for estimating abundance and size of Antarctic predators

“…In our own research programs in the South Shetland Islands, census data on seabirds and pinnipeds could all be collected with UAS methods, providing an archived record of images for future reference. In addition to capturing images for estimating abundance of animals, aerial photographs allow post-processing of morphometrics in target species which can be used to track changes in animal size, body shape, and nutritive condition (Perryman and Lynn 2002;Miller et al 2012). Thus, we wanted to test the feasibility of using a VTOL to estimate size and condition of leopard seals, an apex predator that affects Antarctic populations of penguins and seals (Siniff and Stone 1985;Boveng et al 1998;Ainley et al 2005;Schwarz et al 2013).…”

Body condition changes arising from natural factors and fishing gear entanglements in North Atlantic right whales Eubalaena glacialis

“…Previous studies of right whale body condition, including ultrasonic and photogrammetric measurements, have described changes in condition in relationship to reproductive and energetic demands (Miller et al 2011(Miller et al , 2012. However, no studies to date have characterized how quickly changes in body condition can be detected, or the potential impact of various sources of energetic stressors on that rate of change.…”

Factors influencing heterogeneity in female reproductive success in a Critically Endangered population of bottlenose dolphins

“…Animal condition is likely to change from year to year (Miller et al 2011(Miller et al , 2012, and thus our static (at 2012) length estimate for female dolphins is unlikely to represent a mother's breeding condition for calf births before 2012. While year-to-year breeding condition is an important factor influencing reproductive success (Miller et al 2012), variation in absolute body size among individuals in a population may also be important (Reiter et al 1981, Hussey et al 2010. In Doubtful Sound there is substantial variation in body size among adult dolphins (Chong & Schneider 2001, Brough 2013, providing an interesting opportunity to assess how reproductive success may be influenced by body size in a cetacean species inhabiting a harsh environment.…”

“…Total length is a standard measurement of size in marine mammals which is closely related to total body mass (Trites & Pauly 1998). Animal condition is likely to change from year to year (Miller et al 2011(Miller et al , 2012, and thus our static (at 2012) length estimate for female dolphins is unlikely to represent a mother's breeding condition for calf births before 2012. While year-to-year breeding condition is an important factor influencing reproductive success (Miller et al 2012), variation in absolute body size among individuals in a population may also be important (Reiter et al 1981, Hussey et al 2010.…”

“…Mother size is often correlated with her overall condition and reproductive fitness (Fairbanks & McGuire 1995, Derocher & Stirling 1998. In this study, as mother size was measured as length, and only in 2012; it does not accurately represent breeding condition, which is likely to change over time (Miller et al 2011(Miller et al , 2012). Yet, the fact that variation in absolute body size among female dolphins in Doubtful Sound influences calf survival is an interesting and important result.…”