Nineteenth-century evidence for the Golfo de Panama as a migratory destination for southern humpback whales, including the first mention of singing

The use of the coastal waters of Central America as a wintering ground by some humpback whales (Megaptera novaeangliae) from summer feeding grounds in both the North Pacific and the South Pacific has recently been established. Evidence includes records of calves off Costa Rica in both January and August (Acevedo and Smultea 1995), or during northern and southern winters, respectively, and sightings of whales off Costa Rica or Panama in January/February that were previously photographed off California, mainly between July and October (Steiger et al. 1991, Calombokidis et al. 2000). In the reverse direction, trans-equatorial movements have included inter-year matches between Peru and Colombia, and between Ecuador and Colombia (Flórez-Gonzalez et al. 1998), and long-distance movements from the Antarctic Peninsula and Magellan Strait in summer to Ecuador, Colombia, Panama, and Costa Rica from July through September (Stone et al. 1990, Acevedo et al. 2007).

Most of the above accounts have also referred to the charts of Townsend (1935) on which the positions of catches by nineteenth-century whalers are plotted by month, and which seem to indicate a similar extended seasonal use of Central American coastal waters by humpback whales (Aguilar et al. 1997). However, evidence from the primary records on which Townsend's charts were based has not been included. In this paper, I present information from one of the logbooks that Townsend used in his analysis, and which seems to have been the source of the majority of plots of humpback whale catches shown on his chart in the vicinity of the Golfo de Panama. The logbook is also particularly informative as regards the details of whaling events, and contains the first apparent references to humpback whales singing.

The bark Gay Head of New Bedford (Thomas H. Jenkins, Master) sailed from New Bedford on 26 October 1882 and returned home on 25 June 1887. The results of the voyage are given as 1,400 barrels of sperm oil and 1,750 barrels of whale oil (Hegarty 1959), and an abstract of the voyage (up to December 1885) made by A. C. Watson as part of the study published by Townsend (1935) records the taking of 54 sperm and 40 humpback whales, all in the Pacific Ocean. A page of the abstract must be missing, as Townsend lists a catch of 57 sperm and 50 humpback whales for the voyage. The logbook of the voyage (ref. no. 1869 in Sherman et al. 1986) is lodged in the Providence Public Library (catalog no. 259), a microfilm copy of which I have examined and is the basis for this paper. The identity of the log keeper is unknown. Modern spellings of place names mentioned in the log have been used throughout.

After rounding Cape Horn the Gay Head saw its first whales of the voyage, sperm whales, on 2 April 1883 in the vicinity of the Galapagos Islands. For the next 3.5 yr the vessel stayed in the eastern tropical Pacific, alternating periods of open-ocean sperm whaling with coastal humpback whaling. This pattern included three visits to the Golfo de Panama for humpback whaling, all between late June/early July and September (Table 1). While in the bay, the vessel operated principally in the vicinity of Golfo de Parita, “Liner Rock” (apparently in the mouth of Golfo de Parita), Isla Otoque, Isla Taboga, and Golfo de San Miguel (Fig. 1).

The logbook frequently mentioned the presence of cow–calf pairs in Golfo de Panama—on 17 d in 1883, 20 d in 1884, and 13 d in 1886, or about 23% of the time spent on the ground. Most of these encounters took place in the second half of the season, with 34 (68%) occurring after 15 August. This would be consistent with the normal attendance pattern of southern humpback whales, where females with calves-of-the-year are among the last to leave breeding grounds in spring (Dawbin 1997). Although it is not clear how the whalers were able to distinguish living male humpback whales from females without calves, the logbook also made frequent reference to the presence of bulls on the ground. Although 12 of these instances involved individuals that were struck and lost, so that there was a remote chance they might have been able to establish the sex of the whales when in such close proximity, there were at least another eight occasions when the logbook-writer simply commented “several bulls in sight,” or “seen several bulls.” It is possible the whalers used behavioral cues (whales acting as escorts, for instance, Clapham et al. 1992), or scarring of the dorsal fin area (Lien and Katona 1990), but without further information the accuracy of their sex determinations of live individuals as males must remain uncertain.

On 15 August 1883, the logbook records “At 12 o'clock the SB [starboard boat] struck a singer at 2 o'clock took him along side and commence cutting…” and on 24 July 1886 “At anchor in Parita bay S boat struck a singer went SW cut line.” The use of the word “singer” is interesting, given that the concept of humpback whales producing a “song” did not arise in the scientific literature until the publication by Payne and McVay (1971). Presumably the song was detected through the bottom of the whaleboat as it laid waiting for a whale to surface, as the author has experienced in an aluminum boat. Not too much significance should be attached to the use of the word “him” in referring to the singer, as this was also sometimes used in the logbook for whales otherwise described as “cows.”

Attempts to catch humpback whales were also made at other times during the voyage, notably in the vicinity of Tumbes and Isla Santa Clara in early June and late November 1883, and in mid-August 1885, but these were much less successful, only three whales being processed from nine strikes (Table 1). Between 2 and 21 October 1885, the Gay Head was once again in the same area, cruising off the coast between Punta Santa Elena in the north and 6°15′S in the south. On 13 of the intervening days the logbook recorded sightings of humpback whales, including days of “several” or “plenty” whales and records of at least three cow–calf pairs. Inexplicably, however, no boats were lowered on any day, and no attempted strikes recorded. On 7 October, however, the Captain went ashore at Paita to discharge sick and injured men, so it is possible that with a depleted crew it was decided not to risk whaling.

The timing of the humpback whale catches in the Golfo de Panama in all three years (July to September with a median date of 12 August; Fig. 2) suggests that the Gay Head was exploiting whales from the Southern Hemisphere on their winter migration into warmer waters for breeding (rather than those from the Northern Hemisphere on a similar migration, which should have been in these latitudes between December and March). Similarly, the observations of singing whales on 24 July and 15 August, the apparent abundance of cow–calf pairs and their pattern of attendance, were all more consistent with a southern breeding season than a northern one. Consequently the trans-equatorial movement of southern humpbacks in the eastern Pacific in the austral winter is a phenomenon that seems to have persisted for at least a century.

The failure of the Gay Head to remain on the Central American coast between October and June, when Northern Hemisphere humpback whales should have been in attendance, suggests either that the Master was unaware that they would be there, or that he considered opportunities elsewhere to be potentially more rewarding. It also implies that there was probably a marked drop-off in whale availability between the occurrences of the whales from the two hemispheres, thus reducing the likelihood of the mixing genetically of the two populations.

The logbook also provides valuable data on the processes of nineteenth-century humpback whaling, particularly loss rates (Table 1), data that are essential in reconstructions of the size of historical removals from populations (Mitchell and Reeves 1983). The declared success rate of irons thrown in striking the whale was 81/91, or 89%, although it seems possible that some misses (being somewhat embarrassing) might have gone unreported. Of the 81 whales struck, 57 or 70.4% were killed and 53 or 65.4% successfully processed. The concentration on cow–calf pairs was obvious, and the success rate (26 processed from 31 struck, or 83.9%) was higher for this social grouping than for other classes (27 processed from 50 struck, or 54%). Reasons for losing struck whales also differed: four of the cows with calves sunk after being killed and could not be recovered, whereas for other classes the line parted (eight) or was cut (three), the iron drew (seven) or broke (four), or a boat was capsized (one). Among the other classes, 12 of the struck and lost whales were described as “bulls,” while only three of the processed catch were similarly declared. This suggests that hunting humpback whales with calves was less taxing on gear and personnel than hunting other classes, particularly males, and this may have accounted for their differential targeting.

Sharks proved to be a notable contributor to loss of production. In the Gay Head's logbook there are nine separate references to damage caused by sharks feeding on whales that had been struck and killed, all in Golfo de Panama. On three of these occasions the whale was lost as a direct result of the shark predation: each time the whale had sunk when killed and was subsequently not retrieved (because the lines had been cut or the irons eaten out by sharks) or was too severely damaged to be worth keeping. On another occasion only half the whale could be processed.

The success rate for whaling in the Golfo de Panama (50 humpback whales processed in about 7 mo on the ground) contrasted markedly with the rest of the voyage, in which 57 sperm and another three humpback whales were processed in about 40 mo at sea. Despite their generally low value, humpback whale catch rates of this magnitude must have made the ground a popular one. Whalers spoken on the ground by the Gay Head included the two New Bedford barks John Dawson (Capt T. P. Warren) and Sea Fox (Capt E. G. Gifford), but there were undoubtedly other vessels that preceded and succeeded this voyage. Inspection of any logbooks surviving from such voyages would help confirm the conclusions of this paper.