Reproduction And Rearing
Not much is known about the mating process in Belugas, only that it most likely occurs during the winter or just as the spring migration is beginning.  The gestation period for Belugas in the wild has been estimated at about 14 months, allowing calves conceived towards the end of winter to be born the following spring as the whales return to the warmer and shallower waters (Goetz et al., 2007).From studies of Belugas in captivity (See General information) we have learned much more about reproductive cycles and development.  Beluga cows are seasonally polyestrous having up to two ovulations per season, with an estrous cycle length of 47 days (Robeck et al., 2005).
In captivity conception time was able to be determined to within a two week period , with most conceptions occurring in March, April, and May, which resulted in a mean gestation time of 475 days (15.5 months).  The discrepancy between this estimate and those of wild beluga may be due to the effects of captivity or the methods used to estimate wild gestation periods may be inaccurate (Robeck et. al., 2005).Female food intake increases in the months leading up to the birth (Kastelein et al., 1994), however food intake decreases to zero in the days leading up to and including the birth (Robeck et al., 2005).  After the Birth the cows intake doubles during first few months of lactation as her energy requirements have increased to include her calf’s thermoregulatory needs (Kastelein et al., 1994).
	Carrying a calf 15 months to term is only the beginning of the mother cow’s investment.  There is no involvement of even awareness of the father as he may well be summering in an entirely different location.  Although previous offspring may be around and act as helpers the mother is primarily responsible for all of the calf’s needs.    A study examining the mother –calf relationship conducted in the white sea found the following:
	Calves are born between April and August.  They are initially brown but turn black after about 20 days.  The newborn permanantely follow the mother usually at the side or tail end.  With an newborn the mother will stay close to the surface to facilitate respiration s the newborn still has poor motor coordination.  Feeding always occurs underwater and is preceded by tight physical contact between mother and calf.    By the 4th day calves are allowed to swim up to 3 meters away from the mother but only under “safe” conditions with other cows and calves and no males present.  Although it is not known if infanticide occurs in beluga it is a concern with other marine mammals.  As the calves gain motor function and coordination they move progressively farther from the mother but still maintain positions towards the tail or side.  By one month calves have grown to 1/3 adult size and can hold their breath for up to 3 minutes, their skin is smoother and black and they move around more freely and at greater distances from the mother.  By 2 months the calf is at half its adult size and has turned a dark gray, it no longer requires any help in swimming and has decreased the proportion of time spent at the mother’s side or tail (Krasnova et al., 2006)
Females reach sexual maturity at about 6-8 years.  In captivity most females housed with “experienced” males conceived during their first ovarian cycle at 6 years, and females as old as 20 have successfully conceived (Robeck et al., 2005).  Males reach sexual maturity slightly later, in captivity the youngest males to sire a calf was 9 and the average age was 13.  This figure is probably younger than in the wild due to competition for mates with bigger and more experienced older males in the population.  Peak testosterone levels occur between January and April lending support to the theory that conception usually occurs during the winter and into spring migration (Robeck et al., 2005)

 

 

This website was completed in partial fulfillment of the requirements for biology 323, Animal Behavior, at Davidson College in the Spring Semester 2008.

Site created by Jordan C. Iordanou (joiordanou@davidson.edu)