Depending on the species some whales may travel thousands of miles from their feeding grounds to their mating grounds in order to look for a mating partner or if the female is already pregnant give birth to their offspring. Although some whale species are known to migrate long distances there are a number of species that inhibit the same area throughout the year or follow the migration patterns of their food rather than looking for an ideal mating environment.
The freezing water, diminishing food supply and internal mating clock encourage the whale populations to seek out a new location where they can meet up for their annual mating season, reproduce and bare offspring.
In order to find a more stable environment these whales travel towards the equator where the weather is warmer and produces a suitable environment for mating and having children while also providing some species with better protection from predators due to larger pods formed by mating groups. During the long migration trip some species of whale are known to fast for several months and will live solely off of the fat they stored in their blubber during feeding season.
Once the whales arrive at their breeding grounds and they are ready to mate the male whales begin looking for a mating partner by courting the female whales and competing with other males.
The first phase a male whale goes through when it attempts to find a female mating partner to reproduce with is to attract a female whale during a courtship phase.
During the courtship period unrelated male whales will compete for the right to mate with the female whales first by showing their worthiness, dominance, competitive advantages and strengths.
Some of these courting activities may include breaching Lunging out of the water , fin slapping slapping their fins against the water , singing producing low-frequency melodic tones and giving gifts to the female among other activities and gestures. Although male whales are known to compete among one another for the right to mate with a female it is rare that the whales will cause severe physical harm to one another, at least not with most species.
A few species of whale such as several of the beaked whale species are known to be quite aggressive and may scar other whales or obtain fractured beaks from intense fighting. For a number of whale species it is common for the female to mate with several males in a single season to increase her chances of producing offspring. Low frequency pulses may be used to navigate by creating a sonic image of distant oceanic features.
Little is known about intraspecific communication in these whales. Vision and smell are limited, but hearing is sensitive. The diet of blue whales is principally krill. In southern waters the main species eaten is Euphausia superba , a small less than 7 cm planktonic crustacean that is tremendously abundant. In northern waters the main species are Thysanoessa inermis and Meganyctiphanes norvegica , though other planktonic species and small fish are also eaten.
Adult whales can ingest 3 to 4 tons of krill per day. Blue whales, by virtue of their extreme size, have virtually no natural predators. They were hunted by humans extensively in the 20th century, almost to extinction.
Blue whale calves may be vulnerable to predation by orcas and large sharks. Blue whales, and other large baleen whales, are important predators of krill. Blue whales were formerly heavily hunted for blubber and oil. Because of the immensity of blue whales, only sperm whales approached them in economic importance. A single blue whale could yield 70 or 80 barrels of oil.
Baleen was also an important whale product, valued for its plastic like properties that were applied in a wide variety of products. Blue whales, and other large whales, have important ecotourism value.
Blue whales were not initially among the most heavily hunted species due to their size, speed, and remote habitat. Technological advances from , however, allowed whalers to pursue the species. The estimated total kill of blue whales in the 20th century was , animals. By the 's, blue whales were on the edge of extinction. Estimates of the remaining population range from 2, to 6, individuals and it is not yet clear that the blue whale will escape extinction. Southern hemisphere populations have been surveyed extensively and are estimated at to 1, animals.
Northern hemisphere populations are estimated at about 5, individuals but the scientific rigor of these surveys has been criticized. It is the second largest ocean in the world after the Pacific Ocean. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a now extinct synapsid ancestor; the fossil record does not distinguish these possibilities.
Convergent in birds. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales. Iteroparous animals must, by definition, survive over multiple seasons or periodic condition changes. An aquatic biome consisting of the open ocean, far from land, does not include sea bottom benthic zone. Compare to phytoplankton. Nowak, R. Walker's Mammals of the World. Tinker, S. Blood in veins that go through fins and the fluke loses heat. When that blood is sent directly to the testes, the sperm are cooled below body temperature and remain viable.
The females have a long vulva with two nipples on each side to nourish newborns. They go in heat any time of the year, but the most common is during the migration to warmer waters for mating season. Blue whales reach sexual maturity between the age of 5 and They are dioecious and undergo sexual reproduction. Normally, they migrate near the equator to reproduce. Blue whales undergo a very elaborate mating ritual.
The male and female spend time rolling around each other, then they take a deep dive into the ocean abyss as they continue to communicate with each other. Suddenly, they fly upwards and cross the surface, and as the do the male thrusts the penis into the vulva and ejaculates. Blue whales reproduce via sexual meiosis. The male and female each produce haploid gametes.
Male gametes are sperm, and the female gametes are eggs.
0コメント