Beluga Whales
Reproduction and Development
Reproduction and Development
Reproduction and Traveling Pods
This is a video of belugas demonstrating mating behavior (caressing, swimming in synchronicity). Don't worry - nothing crazy happens :)
Here is a video of a female beluga giving birth!
Belugas seasonally mate and give birth usually in the late winter to early spring (Matthews & Ferguson, 2015). As preparation, males undergo severe fasting to maintain the integrity of their sperm. Females, on the other hand, can reproduce at a relatively young age, but birth rates gradually lower with increasing age. When traveling to breeding grounds, females typically form pods with their maternal relatives and stay in the pod for life, while also helping look after young belugas in the pod. Female belugas with offspring are known as cows, and will stay outside of the mating circles and hide their calf (Krasnova et al., 2006). Once males reach around three to four years of age, they typically leave their mother's pod to join an all-male pod, and will only return to mate.
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Males run after suitable females and engage in big bending motions to push away other potential males from mating with the female. If the female and male both consent, they will swim together and gently touch each other until the female swims under the male's belly to mate. They continue this process while swimming together in harmony (Brooks, n.d.). After copulation, females undergo a period of increased foraging to produce energy-rich milk via lactation. Lactation, which is the most energy-consuming component of the entire reproduction cycle for the female, diverts all maternal resources to the offspring. This strict allocation of resources can risk the mother's later reproductive success and hampers efforts at self-maintenance (Matthews & Ferguson, 2015). Fortunately, the fat content in the milk is not as rich as mysticete milk, so female belugas can stretch the period of lactation (Fedak et al., 2008). After about a 12 to 14.5 -month gestation period, a beluga calf is born.
Nursing Process and Calf Development
Once born, beluga calves are mobile. Due to this adaptation, beluga mothers can feed their young without needing to leave them alone for long periods at a time. The calf's immediate mobility also allows the cow to start teaching them how to swim, learn migratory patterns, and more. Building these skills make escaping predators relatively easy, despite the calves being young. Coupled with the belugas' strong social nature, pods with calves can escape swiftly with increased awareness and defense against predators (Fedak et al., 2008).
There are a range of behaviors the calf exhibits, but right after birth, the calf swims close to the water surface to aid breathing. In addition, newborns that are uncoordinated swim at the mother's side of tail to overcome the water resistance they have yet to build the musculature for (Krasnova et al., 2006). The most common behaviors that the calf exhibits within the first two months of birth is swimming at the cow's side and at the cow's tail for the same reason (Fig. 1).
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Newborns and young calves are entirely dependent on the mother for food, especially for the first couple of years after birth. When hungry, the newborn will beg by initiating very close physical contact - a form of tactile communication - with its mother. By leaning on the cow's tail and rubbing on her sides and back, the cow stops so the calf can feed. As all of the feeding occurs underwater, either the mother or the calf must turn over to feed. The calf will point its beak at a right angle or a 45-degree angle in relation to the mother's belly for four to six seconds at a time (Krasnova et al., 2006). To suckle, either the calf or the mother must hold their breath (if the mother does, she also has to roll on her side) (Fedak et al., 2008).
As the calf reaches two months, however, it becomes more independent and displays more behaviors farther away from its mother (Fig. 2). Notice the big drop in percentage "At the cow's side" (almost a 20% decrease from newborns) and the moderate percentage spent "At the cow's tail" (around a 10% increase compared to newborns). As mothers and their young are often in pods with other females and calves, mothers may rest on the seafloor and allow for their two-month-olds to play around with each other, thus encouraging more independence. This encouragement toward independence urges the calf to learn about many dangers and the necessary behaviors and skills that will keep them alive. Additionally, two-month-old calves also start to lean on or rub the mother's head. While this behavior is recognized in dolphins as a type of social activity, this should not be confused with the more aggressive "butting" behavior that belugas exhibit to establish a hierarchical position (Krasnova et al., 2006). Calves that "butt" the mother's head is a merely a demonstration of observational learning of adult beluga behavior.
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The calves usually follow the mother for one to two cycles to the breeding and molting grounds to learn the migration patterns. After around three years or four years, female belugas can become sexually mature, while males become mature at around seven years of age (Brooks, n.d.​). As the calves age, their body skin changes from gray to their iconic white color (Williams, 2002).
Figure 1: These are the multiple positions a calf (gray) may assume in relation to its mother(white). The "at the cow's side" behavior is pictured at the top left corner, and the "at the cow's tail" is pictured at the bottom left corner.
Figure 2: Above is the comparison of the different behavioral elements shown in Figure 1 across newborns, 1-month and 2-month-olds. Notice that the gradual decrease in percentage of the time spent "At the cow's side" and "At the cow's tail" signifies the calf's growing independence.
Picture Credits and Licenses - Title Image (scaled to fit into column): Sheila Sund from Salem, United States, CC BY 2.0, via Wikimedia Commons