Short-finned pilot whale

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). A 2014 study found a unique haplotype in the Caribbean region. Evolution 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. ==Description==

Short-finned pilot whales are black to dark gray/brown, with a thick tail stock, fluke with sharply pointed tips, bulbous head, and a broad, sickle-shaped dorsal fin. Coloration typically includes light grey to white areas such as a saddle patch behind the dorsal fin, a light grey or white anchor-shaped patch under the chin and belly, and a blaze marking behind the eye. Short-finned pilot whales can reach up to in length and weigh up to , making it the third-largest species of oceanic dolphin, behind the orca and long-finned pilot whale. When they are born, short-finned pilot whales weigh about at a length of . 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. == Geographic distribution ==

, Canary Islands Short-finned pilot whales are found in both coastal and pelagic waters in temperate and tropical regions of the Indian, Atlantic, and Pacific Oceans. Information on the spatial habitat use of pilot whales in the northwest Atlantic is limited, however short-finned pilot whales are thought to range from the southern end of Georges Bank into the tropics, overlapping with the range of the long-finned pilot whales along the mid-Atlantic shelf break between Delaware and Georges Bank. Once commonly seen off of Southern California, short-finned pilot whales disappeared from the area after a strong El Niño year in 1982 and 1983, and have since been encountered infrequently, primarily during warm-water years such as 1991, 1993, 1997, 2014, and 2015. Many countries offer safe whale-watching guidelines designed to minimize the impact of their activities on the animals being watched (see supplementary materials). ==Behaviour==

off of Guam Social lives Short-finned pilot whales are long-lived, slow to reproduce, and highly social animals. They are usually found in pods of 10 to 30 individuals, though groups of up to several hundred short-finned pilot whales have been reported in the Caribbean. These pods are stable social structures, meaning that they form hierarchical associations that remain stable for generations, and are primarily thought to be matrilineal, i.e. led by an elder female relative, similar to those of resident killer whales. Groups of closely related individuals formed tight associations, or clusters, with other close relatives, and genetic analysis revealed a significant differentiation between clusters, even those that were present in the same area. Clusters that were more genetically different also spent less time together. This could suggest that social behaviour in short-finned pilot whales inhibits gene flow outside of family groups. Pilot whales are also known for their socializing and playful behaviour at the surface, such as lobtailing (slapping their flukes on the water surface) and spy-hopping (poking their heads above the surface). Members of a pod have also been observed making various altruistic behaviours, such as alloparental care, in which nonparent whales help to take care of young that are not their own. In the closely related long-finned pilot whales, babysitting of calves by other group members is frequently documented, and can be performed by males as well as females. Reproduction Males are polygynous, meaning they will mate with multiple females at one time and throughout their lives. Pods are often found with around one mature male per every eight mature females. During mating aggregations, males will temporarily leave their pods to mate with females from other pods, but will return to their own pods once mating is over, which helps to prevent inbreeding. The diet preferences and foraging habits of short-finned pilot whales are still poorly understood, however, they are known to be deep-divers, and are generally found foraging on the steep slopes along the continental shelf break. On rare occasions, they are also known to prey on other marine mammals. They use echolocation when they hunt, clicking and listening for echoes from prey as they descend and generating a rapid "buzz" of clicks at the depth of their dive that accompanies a high-speed sprinting attack. ==Population status==

The total of all available abundance estimates for short-finned pilot whales is approximately 700,000 individuals, but populations vary worldwide, and large parts of the species' range have not been surveyed, therefore actual abundance could be considerably greater than this. 7,700 individuals are reported in the eastern Sulu Sea (Philippines), and in the Eastern tropical Pacific the most recent estimate from 2000 gives 589,000 individuals. The resident population in Tenerife, Spain, is estimated at only 350 individuals. Three stocks of short-finned pilot whales are recognized in U.S. waters, which live along the east and west coasts, and around the Hawaiian Islands. There are no population estimates for the different island communities, but in all of Hawaiian waters there are an estimated 90-20 thousand short-finned pilot whales, with the MHI community being the most abundant. Short-finned pilot whales are among the most frequently encountered cetaceans in the Canary Islands, but estimates of abundance are not available. Records suggest they are also abundant in deep water off the west coast of Africa, around the Maldives, and in the northern Indian Ocean more generally. However, despite previous study efforts, there is still no information on global numbers or trends for this species. ==Threats==

Natural predators and strandings . One study suggests short-finned pilot whales are among Caribbean Orcas' prey, and Killer Whales have been recorded attacking short-finned pilot whales in Peru. 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. Human-induced threats includes a skewer of fried whale meat (left) and a bowl with grilled meat over rice, topped with pickled ginger (right). Short-finned pilot whales have been hunted for many centuries, particularly by Japanese whalers. Today, pilot whales are hunted in a few areas of Japan, mainly along the central Pacific coast, as well as the Lesser Antilles (e.g., St. Vincent and the Grenadines, St. Lucia, Dominica, Martinique), where whales are commercially hunted and the meat is available for human consumption. Pilot whales' strong social bonds and herding instincts make them prime candidates for so-called drive fisheries, where whales are herded towards shore by boats and then killed in shallow waters. Other hunting methods include hand or crossbow-projected harpooning, and small-type whaling (defined as the use of a cannon mounted on a vessel below a certain size). From 2010 to 2023, the average annual catch of short-finned pilot whales in Japan was 73 whales, a large proportion of which was allocated to the drive hunt in Taiji. Certain Japanese restaurants serve pilot whale as sashimi, or as steaks that are marinated, cut into small chunks, and grilled. The meat is high in protein and low in fat (a whale's fat is contained in the layer of blubber beneath the skin). It is considered integral to certain cultures. Short-finned pilot whales off the west coast of the US were found to have high amounts of DDT and PCB, however the levels were lower in whales from Japan and the Antilles. Captivity , 1962 Short-finned pilot whales, have been kept in captivity in various marine parks off southern California, Hawaii and Japan, arguably starting the late 1940s. Pilot whales have historically had low survival rates in captivity, with less than half surviving past 24 months. Bubbles, a female short-finned pilot whale who was displayed in Marineland, and eventually at Sea World California, was one exception to the rule, living to be somewhere in her 50s when she eventually died on 12 June 2016. Climate change In the context of global warming, the ranges of short-finned pilot whales are expected to shift northward in response to warming temperatures, which could eventually lead to increased overlap and potential hybridization with their long-finned cousins. The distribution limit of short-finned pilot whales in the Northeast Atlantic has already shifted 3° latitude in only two decades, and evidence for introgressive hybridization (i.e. the movement of a genes from one species into the gene pool of another) with long-finned pilot whales is appearing in DNA samples from the Northeast Atlantic. Like many other species, pilot whales are also likely to be affected by changes in prey distribution and abundance, habitat degradation, and other secondary effects of climate change, coupled with human-mediated stressors such as marine traffic and pollution, which could lead to the global decline, or even loss, of this species. ==Conservation==

The short-finned pilot whale was listed on the IUCN Red List as Data Deficient in 2008, and remains data-poor in much of its range, especially in the Southern Hemisphere and in large parts of the tropical and warm temperate North Atlantic Ocean. and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). The purpose of these two groups is to reduce threats to cetaceans through improving current knowledge, and enforcement of the outlined conservation measures. The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU) and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU). In the United States, short-finned pilot whales are protected under the Marine Mammal Protection Act. Globally, they are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), which aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Around the world, several efforts aim to address the threats faced by cetaceans, including pilot whales. For example, in the United States, NOAA Fisheries implemented the Pacific Offshore Cetacean Take Reduction Plan, which aims to reduce serious injuries and deaths of marine mammals incidental to the California/Oregon thresher shark/swordfish drift gillnet fishery through methods like gear modifications, limited fishing depth, and skipper education workshops. In areas where resident pilot whale populations are seen near the coast, such as those off the Canary Islands, Madeira, and Hawaii, they can be studied using photo-identification. This technique helps researchers identify unique markings and scars on the whales' dorsal fins, which are used to recognize individuals from photographic surveys to monitor movements and life histories over time. Other research techniques including satellite tagging, acoustics, and genetics to learn about the species' long-range movements, genetic diversity and social behaviour. However, there have been few long-term studies focused on this species, and data is spotty for many of the small local populations. This makes assessing threats and population dynamics difficult, and more research is needed before any statements can be made on the global status of short-finned pilot whales. ==See also==