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dwarf sperm whale

Dwarf Sperm Whale 




About the Species

The dwarf sperm whale is a toothed whale named after the waxy substance, spermaceti, found in its head. This organ is a sac of oil that helps the whales produce sound. Similar to squids, dwarf sperm whales can produce a dark, ink-like liquid that helps them escape from predators.

Dwarf sperm whales are found in temperate and tropical seas worldwide. The dwarf sperm whale appears very similar to the pygmy sperm whale. In the field, it is very difficult to distinguish between the two species because they can be so easily confused. Both species are poorly known due to the limited availability of information and their cryptic appearance at sea.

Dwarf sperm whales, like all marine mammals, are protected under the Marine Mammal Protection Act. NOAA Fisheries and its partners are working to conserve dwarf sperm whales and further our understanding of this species through research and conservation activities.

Population Status

NOAA Fisheries estimates population size in its stock assessment reports.

Dwarf sperm whales usually avoid vessels and planes, the tools that our scientists use to measure population size. Additionally, due to their cryptic nature, it is difficult to see these whales when they surface to breathe unless sea and weather conditions are very calm. As a result, scientists rarely see dwarf sperm whales at sea. This makes it difficult to estimate their minimum population size or current population trends.

Appearance

Dwarf sperm whales have a small, compact body with a small dorsal fin located near the middle of their back. Each individual whale’s dorsal fin is a slightly different shape. While on the water’s surface, dwarf sperm whales have a low profile because their head and back are somewhat flat. Their head is sometimes described as shark-like because of its pointed snout and narrow, underslung lower jaw. They have a marking behind the eye that is often called a "false gill" because it looks similar to a fish's gill cover or slit.

Dwarf sperm whales have a brown to blue-gray colored back. Their underside is paler with white or pink tones. They have up to three pairs of teeth in the upper jaw and seven to 13 pairs of teeth in the lower jaw. Their eyes are dark and bulging with a dark ring surrounding them.

Dwarf sperm whales can sometimes be confused with pygmy sperm whales, their closest relative. These two types of whales were not distinguished as separate species until 1966. In the wild, it is very difficult to distinguish between the two species because they have similar appearances and geographic ranges.

Behavior and Diet

Dwarf sperm whales are usually seen either alone or in small groups of 16 or fewer individuals. These groups can vary based on age and sex, but little else is known about their social organization.

Dwarf sperm whales spend very little time at the water’s surface and almost never approach vessels. When they are seen at the surface, they are usually either swimming slowly or lying still (also known as logging). Their blows are not visible when they surface. They will slowly sink and disappear from view without showing their flukes before diving back into the water.

Dwarf sperm whales’ use of the "squid tactic" makes them unique among whales. Each dwarf sperm whale has a sac filled with dark liquid in its intestine. The whale can release more than three gallons of dark, reddish-brown liquid—or ink—from this sac. This liquid creates a dark cloud in the water to help protect the whales when they feel threatened or when they are trying to escape predators.

Dwarf sperm whales can dive at least 1,000 feet deep in search of food. They may feed in slightly shallower waters than pygmy sperm whales. They eat cephalopods (e.g., squid and octopus), crustaceans (e.g., crabs and shrimp), and fish. Like bats, and other toothed whales, dwarf sperm whales use echolocation to locate prey, meaning they use sound to navigate and "see" the world around them. They do so by producing sounds from their melons (or foreheads) that reflect off of the objects around them.

Where They Live

Dwarf sperm whales live in temperate and tropical seas around the world.

In the United States, dwarf sperm whales live in the waters of Hawaiʻi, the Pacific Northwest and California, the western North Atlantic, and the northern Gulf of Mexico. They may be more common off the southeastern coast, as more strandings have happened in this area. Dwarf sperm whales are also the sixth most commonly seen toothed whale around the Hawaiian Islands.

In the Southern Hemisphere, dwarf sperm whales live in the waters around Australia, New Zealand, Indonesia, Chile, southern Brazil, and South Africa. In the Northern Hemisphere, they live in the waters around Oman, the Persian Gulf, the Maldives, Japan, British Columbia, the Gulf of California, the Gulf of Mexico, and northwestern Europe. Their migration patterns are currently unknown.

Lifespan & Reproduction

Dwarf sperm whales can live up to 22 years. They reach sexual maturity when they are 2.5 to 5 years old. In the Southern Hemisphere, females give birth between December and March. Females may give birth after a pregnancy that lasts about 1 year. Calves are about 3.3 feet long and weigh about 30 pounds at birth. They are weaned after 1 year.

Threats

Entanglement in Fishing Gear

One of the main threats to dwarf sperm whales is becoming entangled or captured in commercial fishing gear such trap lines, pots, and gillnets. Once entangled, they may swim for long distances dragging attached gear, potentially resulting in fatigue, compromised feeding ability, or severe injury. These conditions can lead to reduced reproductive success and death.

Vessel Strikes

Accidental vessel strikes can injure or kill dwarf sperm whales. Dwarf sperm whales are vulnerable to vessel strikes throughout their range, but the risk is higher in some areas with heavy ship traffic.

Marine Debris

Like many marine animals, dwarf sperm whales can ingest marine debris. Debris in the deep scattering layer where dwarf sperm whales feed could be mistaken for prey and incidentally ingested, leading to possible injury or death.

Some stranded dwarf sperm whales have been found with plastic and other garbage blocking their stomach. Stranded whales have also been found with heart disease, immune system problems, and parasite infestations.

Ocean Noise

Underwater noise pollution can interrupt the normal behavior of dwarf sperm whales, which rely on sound to communicate. As ocean noise increases from human sources, communication space decreases—the whales cannot hear each other or discern other signals in their environment as they used to in an undisturbed ocean.

Different levels of sound can disturb important activities, such as feeding, migrating, and socializing. Mounting evidence from scientific research has documented that ocean noise also causes marine mammals to change the frequency or amplitude of calls, decrease foraging behavior, become displaced from preferred habitat, or increase the level of stress hormones in their bodies. If loud enough, noise can cause permanent or temporary hearing loss.

Disease

Stranded whales have also been found with heart disease, immune system problems, and parasite infestations.

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