Balaenoptera edeni

Geographic Range

Bryde’s whales ( Balaenoptera edeni ) can be found in the Pacific, Indian and Atlantic oceans, but they are most commonly found in tropical and sub-tropical regions. These whales have not been found beyond 40° in either hemisphere. Due to their warm water preference, they have been observed migrating towards the equator in the winter. Some small populations are known to be sedentary, including a small population of about 12 individuals along the coast of California. Molecular evidence has suggested that the smaller coastal whales may be a different species than the larger whales that live in deeper waters.

• Biogeographic Regions
• nearctic nearctic
  • native native
• oriental oriental
  • native native
• ethiopian ethiopian
  • native native
• neotropical neotropical
  • native native
• australian australian
  • native native
• indian ocean
  • native native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

• Other Geographic Terms
• cosmopolitan cosmopolitan

Habitat

Bryde's whales live in warm oceanic waters, with temperatures ranging from 15 to 20 degrees C. They are coastal and pelagic creatures that usually follow their food sources. While pursuing prey, they have been observed diving as deep as 300 m.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

Bryde's whales are small rorquals, whales of family Balaenopteridae , whose males range in size from 12 to 13 m, while females are slightly larger, ranging from 13 to 14 m. Both sexes weigh 13,600 to 15,000 kg. Their body is a dark smokey grey above, which then diffuses into a white below. Circular scars from lampreys and cookiecutter sharks have been spotted on the more migratory individuals. With a V-shaped rostrum, their head occupies 25% of their body and has 3 ridges on the top that run from the tip of their snout to the front of their blowhole. Underneath, 54 to 56 throat grooves lie between each flipper and extend beyond their navel. Inside their mouth, 285 to 350 slate gray coarse baleen plates are found on each side, the longest plate is 40 cm. Bryde's whales have 54 to 55 vertebrae, along with 13 to 14 broad, thin ribs; the first rib is double-headed. Their dorsal fin is slightly curved or hooked, while the other fins are short, narrow, and pointed. Their flukes are wide and occupy 24% of the body length. Older research had recognized a pygmy version of Bryde's whales, but since 2003 they have been classified as their own distinct species, Omura's whales . Physically, juveniles have similar characteristics.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Research is lacking on the mating system of Bryde's whales. It is assumed that their breeding behavior is comparable to other related cetaceans .

Bryde's whales reach sexual maturity when they are 10 to 12 m long and 10 to 13 years old. The sedentary, inshore whales conceive throughout the year, while the more pelagic, offshore whales breed more often in the fall months. Much like other whales, their ovulation is spontaneous. Gestation lasts for 11 to 12 months, the first 4 months of pregnancy involves slow fetal development, while the remaining development is considerably faster. At birth, calves have an average length of 3.4 meters and weigh approximately 900 kg. Females have one calf per breeding season, and nurse the calf for 6 months. Females have a 6-month recovery period after the calf reaches maturity at 6 months of age, as evidenced by births occurring every other year.

• Key Reproductive Features
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Females nurse their calves for 6 months, with no paternal influence. At the end of the weaning period, the mother leaves the calf to fend for itself.

• Parental Investment
• precocial precocial
• female parental care female parental care

Lifespan/Longevity

In the wild, Bryde's whales can live 50 to 70 years, the oldest recorded individual was 72 years old; nothing is known about their lifespan in captivity.

Behavior

Bryde's whales are mostly solitary. Those living near the shore may have feeding groups of 15 or less, while those living off-shore may have groups of up to 30. When they travel, 93% of Bryde's whales are solitary, a much greater percentage than the closely-related sei whales . However, Bryde's whales feed with many other whale species, interacting inter- and intra-specifically without aggression while feeding. Although it is uncommon for these whales to produce a visible blow, when they do, it is 3 to 4 m tall and narrow. Their dives usually last 5 to 15 minutes, with a maximum of 20 minutes. Bryde's whales most commonly swim at 1.6 to 6.4 km/h, but they have been recorded to reach 19 to 24 km/h.

• Key Behaviors
• motile motile
• migratory migratory
• sedentary sedentary
• solitary solitary

Home Range

Movements within their primary, or home range, depend on the presence of food rather than breeding. Bryde's whales do not defend a territory.

Communication and Perception

Bryde's whales have been recorded emitting short, but loud, low-frequency moans. Most of the sounds they produce include two types of calls emitted simultaneously. They can repeat these calls every 1 to 3 minutes, and many are produced while the whales are moving. Whales call back and forth, and the type of calls differ with the size of the group. Baleen whales, unlike toothed whales, are not known to echolocate, but researchers have found fat pockets in the ears of baleen whales that are known to help toothed whales echolocate. Although they likely have no sense of smell, their vision and hearing appear to be similar to that of other cetaceans .

• Communication Channels
• acoustic acoustic

• Other Communication Modes
• mimicry mimicry
• choruses choruses
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• ultrasound ultrasound
• chemical chemical

Food Habits

Bryde's whales are unique among other whales with their generalist diet, which enables them to stay year-round in warm waters where they can always find food. As baleen filter-feeders, they use multiple strategies for feeding, including bubble nets, skimming, and lunging. Although there is no evidence of communication while feeding, multiple whales are usually found in the same feeding location. Bryde's whales have also been seen cleaning up after other predators by ingesting the leftovers. The inshore groups prefer fish, specifically anchovies, sardines, mackerels, and herring, while the offshore groups eat copepods and krill of genus Euphausia . They also ingest cuttlefish, squid, and octopi. Each whale generally eats about 660 kg a day, which equates to about 4% of their body weight.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
• planktivore planktivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans
• other marine invertebrates
• zooplankton zooplankton

• Foraging Behavior
• filter-feeding filter-feeding

Predation

Researchers have witnessed predation by killer whales and shark species. When Bryde's whales are approached or pursued by a predator, they try to quickly swim away.

Ecosystem Roles

Due to presumed impacts of intense whaling efforts, we do not know the true ecological impact of these large whales. Bryde's whales host several parasitic species including parasitic worms, commonly called helminths. Other species found on these large whales are sea lice , copepods , amphipods , barnacles , and sea lampreys . Unlike the other species, sea lampreys can cause death, due to organ failure caused by infections or blood loss.

Economic Importance for Humans: Positive

Although whaling is illegal in many parts of the world, there are still countries that have not adopted any laws concerning this practice. The International Whaling Commission was started in 1986 to help eliminate the hunting and killing of whales for their meat, oil, and bones. Common minke whales are the primary hunted species, but Bryde's whales look very similar and often are caught. In the western North Pacific, it is estimated that from 1911 to 1987, 20,000 whales were caught annually, while in South Africa an estimated 2,000 whales were caught from 1911 to 1967.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse effects of Bryde's whales on humans.

Conservation Status

Due to the lack of research on abundance and distribution, Bryde's whales have been named "Data Deficient" on the IUCN Red list. According to CITES, Bryde's whales are classified as Appendix I, the most endangered species, but applications have been put in to move them to Appendix II, animals that are not threatened now but may become so if they are not watched closely. Bryde's whales are protected under the Marine Mammal Protection Act (MMPA), which prohibits the removal of marine mammals from U.S. waters and their importation into the U.S. Real and perceived threats to this species include whaling (legal and illegal), run-ins with ships, and the yet-unknown effects of human-caused noises (including sonar), which have caused the beachings and deaths of whales and other cetaceans . Whaling harvests are sometimes hard to calculate because Bryde's whales are often grouped with similar-looking species. However, reports indicate that an active whaling country, Japan, lied about its Bryde's whale harvest to remain under the catch limits. Specifically, a 1981 to 1987 harvest report from Japan indicated that 2,659 whales were caught, when they actually harvested over 4,000. Therefore, despite international laws and treaties, this species may still be at risk from illegal over-harvesting.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Jessica O'Grady (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Texas State University.

References

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