Interesting Creatures… The Short-finned Pilot Whale (Globicephala macrorhynchus)

Feb 09, 2020 Interesting Creatures in Guyana, News

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The short-finned pilot whale (Globicephala macrorhynchus) is one of the two species of cetaceans in the genus Globicephala, which it shares with the long-finned pilot whale (G. melas). It is part of the oceanic dolphin family (Delphinidae), though its behaviour is closer to that of the larger whales.
It has a worldwide distribution, with a global population of about 700,000, and there may be three or four distinct populations–two in the Pacific, and one in The Atlantic and Indian Oceans. Its range is moving northward due to global warming.
In the Pacific, males average 4–6 m (13–20 ft.), and females 3–5 m (9.8–16.4 ft.). It generally has a stocky build with black to dark grey/brown skin, and can be distinguished from its counterpart by shorter flippers, fewer teeth, and a shorter beak. They are thought to pursue fast-moving squid typically at a depth of 700 m (2,300 ft.), but the maximum recorded depth is 1,018 m (3,340 ft.).
The short-finned pilot whale has been reported as being highly playful and social. It typically travels in pods of 10–30 members, typically family, but has been observed moving in groups of several hundred. Like killer whales, it has a matrilineal social hierarchy with an elder female at the head, and a sizable post-reproductive lifespan. It is polygynous, and females often outnumber males 8:1 in a pod.
Pods are known to mass strand, possibly due to sheer accident, geomagnetic anomalies affected biosonar, injury from loud military sonar, or disease. It was historically whaled, and is still whaled today by Japan and the Lesser Antilles, but is protected by several international treaties.
The name “pilot whale” originated with an early theory that pods were “piloted” by a leader. Other common names include the “pothead whale” (after the bulbous melon), and “blackfish” (a catch-all term used to designate numerous species of small, dark-colored toothed whales, including the pygmy sperm whale and false killer whale).
Worldwide, the diversity of mitochondrial DNA in short-finned pilot whales is considered to be low relative to other species with global distributions. A 2014 study found a unique haplotype in the Caribbean region.
The short-finned pilot whale is considered to be a single species with three divergent types: the Shiho, Naisa and Atlantic short-finned pilot whales.
Long-finned and short-finned pilot whales are often hard to tell apart. However, as their names indicate, short-finned pilot whale flippers are shorter than those of the long-finned pilot whale, measuring about 1/6th of the body length. Short-finned pilot whales also have fewer teeth – 7–9 in each row – and a shorter and broader rostrum with a premaxilla that covers more of the maxilla.
Both species exhibit sexual dimorphism and have similar lifespans of about 45 years for males and 60 years for females, with long-finned pilot whales being generally larger than short-finned pilot whales. The two species have limited overlap worldwide; long-finned pilot whales are found in cooler temperate waters, while the distribution of short-finned pilot whales is largely tropical and subtropical.
There are no documented cases of natural predation on pilot whales, although the species could occasionally be targeted by killer whales or large sharks. Most of the data on pilot whale mortalities comes from mass stranding events. Pilot whales are often involved in mass strandings throughout their range, with several well-documented incidents involving dozens of individuals in Australia, the Canary Islands, and the U.S.
Many theories have been proposed to explain these events, which include accidents in navigation that lead animals to unexpectedly shallow waters, anomalies in the earth’s geomagnetic fields impacting navigation, injury or disorientation caused by military sonar, or impaired navigation in diseased individuals that lead the rest of the group astray.
Due to their tight social bonds, rescue attempts following strandings are not always successful, as whales will often re-strand themselves upon hearing the calls of their group members on shore. Stranding rescue is often difficult and dangerous work, and all individuals witnessing a stranding should contact local authorities to report the incident immediately.
Pilot whales are, however, economically important in the whale-watching industry of some areas of the world, such as Madeira, Hawaii, and the Canary Islands, which host resident populations of these whales.
The effects of tourism activities on pilot whales have not been well studied, but some evidence suggests that the impact of underwater noise from whale-watching boats can have the potential to significantly disrupt communication at close range. Many countries offer safe whale-watching guidelines designed to minimize the impact of their activities on the animals being watched. [Source: Wikipedia]

 

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