SHORT-FINNED PILOT WHALE
Globicephala macrorhynchus Gray 1846

Order Cetacea : Family Delphinidae

DESCRIPTION. A rather large, black delphinid with globose head, no beak, and a bulbous swelling on the forehead in adults; dorsal fin far forward on body, beginning about on plane with back of pectoral fins; pectoral fins long and narrow, about one-fifth of body length; mouth oblique; teeth large, about 10 mm in diameter, 20 mm high, conical, incurved, placed only in anterior part of jaw, and numbering 8–10 in each tooth row. External measurements: total length of male, 4.72 m; tip of snout to dorsal fin, 1.37 m; tip of snout to pectoral fin, 838 mm; length of pectoral fin, 864 mm; breadth of flukes, 1.07 m.

DISTRIBUTION. Short-finned pilot whales are found in warm temperate to tropical waters worldwide, generally in deep offshore areas. They are common in the Gulf of Mexico and numerous stranding and sighting records are available from Texas.

SUBSPECIES. Currently regarded as monotypic, although the taxonomic status of the species is unsettled and requires further research.

HABITS. Short-finned pilot whales may congregate in large numbers offshore; schools of several hundred have been observed, but group size usually ranges from 10 to 60. They are seen inshore at infrequent intervals and occasionally become stranded by severe storms. In fact, they are among the most frequently stranded of cetaceans and often mass strand. These dolphins have mass stranded 15 times in the Gulf of Mexico, although none of the events occurred in Texas. Pilot whales are highly communicative and make a variety of sounds, including noises described as squealing, whistling, loud smacking, whining, and snores. They probably are excellent echolocators.

The food habits of pilot whales are not well known. In the wild they feed on squid and fish; a captive whale consumed 20 kg of squid per day. This particular whale showed no interest in the fish fed to dolphins in the same tank.

Breeding and calving take place in winter. Gestation lasts about 12 months. Calves are about 1.4 m long at birth and weigh approximately 59 kg. Females are believed to give birth only once every 3 years. These whales live in stable, female-based matrilineal societies; postpartum lactation may indicate that older mothers are taking care of young that are not their own.

POPULATION STATUS. Common; strandings and observations. In total, 64 reliable records of short-finned pilot whales are available from the historical record prior to the GulfCet program. Fifty were stranded from the Florida Keys and the Florida west coast; the remainder were from Louisiana, Texas, and the Yucatan Peninsula in southeastern Mexico. During the GulfCet surveys, these whales were sighted 15 times by ship and 12 times by air during all seasons; group size varied from 2 to 85 animals. Sightings were mainly in the central and western part of the GulfCet study area, generally in water 200–1000 m (656–3,281 ft.) deep on the continental shelf slope. Abundance has been estimated at about 1,700 animals in the entire northern Gulf.

Interestingly, stranding records have declined dramatically over the past decades. Short-finned pilot whale reports accounted for 7.1% of all cetacean strandings in the historic record (before 1978); only 4.1% of the record between 1978 and 2001; and none for the period from 2002 to 2014. Given the increased awareness of cetaceans in the past two decades, coupled with the appearance of stranding networks specifically organized to document reports of cetaceans, the modern record should show an increase in sighting and stranding reports if population levels remained stable. These figures should not be cited as evidence of a steep decline in population numbers, but neither should they be ignored.

CONSERVATION STATUS. Short-finned pilot whales are not listed as threatened or endangered by the USFWS, but they are listed by TPWD as threatened. The IUCN gives their status as "data deficient; population unknown," with primary threats given as entanglement in fishing nets and noise. Although certainly not conclusive, the available evidence suggests the possibility of declining populations of these whales in the Gulf of Mexico. For this reason, they bear careful watching in the future.

 

From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.