ACS Research Committee Report

DIVE BEHAVIOR OF RESIDENT KILLER WHALES
Source: Baird, R.W., Hanson, M.B., and Dill, L.M. 2005. Factors influencing the diving behaviour of fish-eating killer whales: sex differences and diel and interannual variation in diving rates. Can. J. Zool. 83: 257-267.

This study was conducted on the resident killer whale population of Washington, U.S., and British Columbia, Canada, between 1993 and 2002. The diving behaviour of killer whales was analyzed with 34 deployments of suction-cup time-depth recording (TDR) tags. The authors hypothesized that dive rate (number of dives per hour) of resident killer whales varied between males and females, with age, between night and day, and among pods. They found that dive rates did not change with age or sex, or between pods. However, when looking at adults only, males dove significantly more often than females during the day. For all whales, dive rates and swim speeds were greater during the day than at night, suggesting that activity levels decline at night.   

CODA PLAYBACKS TO SPERM WHALES IN CHILE
Source: Rendell, L. and Whitehead, H. 2005. Coda playbacks to sperm whales in Chilean waters. Mar. Mamm. Sci. 21(2): 307-316.

Codas are short, stereotyped patterns of clicks produced by sperm whales during social behaviors. Long-term social groups of female and juvenile sperm whales demonstrate consistent patterns in coda usage. Social groups in the Eastern Tropical Pacific belong to one of five vocal “clans” that each have their own coda dialect. There is a question over the use of these codas. The authors hypothesize that groups of female and juvenile sperm whales would respond vocally to coda playbacks and that sperm whales respond differently to coda playbacks of their own clan than of other clans. They played the sounds of codas to groups of whales off of northern Chile. Playbacks were only conducted when whales were at the surface and involved in resting or socializing. Vocalizations from a group of whales in the 15 seconds immediately prior and immediately following a playback were used as a means to quantify a reaction to playback sounds. Playbacks were conducted to four groups of sperm whales on five days. None of the statistical tests yielded significant results. There was little consistent response and also a wide variation of sounds produced. When a reaction was noted, it was most often a cessation of coda production. The authors conclude that the absence of a consistent response indicates that the playbacks did not stimulate the whales and perhaps were not perceived as other sperm whales at all. In the future, other response measures will also be tested to determine if there are reactions that were not perceived here.  

PHOTO-IDENTIFICATION OF FIN WHALES OFF NOVA SCOTIA, CANADA
Source: Coakes, A., Gowans, S., Simard, P., Giard, J., Vashro, C., and Sears, R. 2005. Photographic identification of fin whales (Balaenoptera physalus) off the Atlantic coast of Nova Scotia, Canada. Mar. Mamm. Sci. 21(2): 323-326.

Fin whales in the Northwest Atlantic are commonly sighted in the Gulf of Maine, Bay of Fundy, Gulf of St. Lawrence, and offshore areas of Nova Scotia. Fin whales are only occasional visitors (zero to four sightings per year) to the coastal waters of Halifax, Nova Scotia during the summer. However, in 1997, there were an unusually high number (110) of fin whales encountered. Fin whales in this area were photographed between June and October of 1997 from a whale watching vessel. Individual whales were compared to catalogs of fin whales in other Northwest Atlantic study areas. Thirty-six individuals were identified using the pigmentation pattern on the right side of the animal. Nine of these were previously sighted in the Gulf of Maine and the Bay of Fundy. Three individuals were previously sighted in the Gulf of St. Lawrence. One individual was matched to both the Gulf of Maine and the Gulf of St. Lawrence catalogs. This unusual year of fin whale sightings in the coastal waters of Nova Scotia was most likely due to prey abundance in this area. Commercial catches of herring were up to 6.8 times higher in this area in 1997 than in the following two years. In addition, fishermen also noted a high level of sand lance and krill than in other years. This study suggests that the fin whales from the Gulf of Maine and the Gulf of St. Lawrence intermingle during the summer.  

ENVIRONMENTAL FACTORS RELATED TO CETACEAN MASS STRANDING SITES IN FLORIDA
Source: Walker, R.J., Keith, E.O., Yankovsky, A.E., and Odell, D.K. 2005. Environmental correlates of cetacean mass stranding sites in Florida. Mar. Mamm. Sci. 21(2): 327-335.

The causes of cetacean mass strandings are mostly unknown, but there are many theories, including bottom or geomagnetic topography, auditory trauma, or coast configuration. One possible factor related to mass strandings is wind currents. Coastal upwelling occurs in the Northern Hemisphere when wind blows with the coast on its left, driving surface water offshore and bringing deeper water to the surface near the coast. Downwelling occurs during the opposite conditions. On the west coast of Florida, the prevailing winter winds are favorable for upwelling. On the other hand, prevailing summer winds are favorable for downwelling on the west coast and upwelling on the east coast of Florida. The total number of mass stranding events were recorded for each month and also for each season between 1977 and 2001. Short-finned pilot whales mass stranded more often than other species, but there was no significant seasonal difference between species. Of the 76 stranding events in the study, 21 occurred on the east coast, 23 in the Keys, 12 on the Panhandle, and 20 on the southwest coast. The east coast and Panhandle had more strandings in the winter, while the southwest coast and the Keys had more in the summer. These seasons coincided with the occurrence of downwelling-favorable conditions. No mass stranding events occurred during extended upwelling-favorable winds. In all of the east coast records, a change in wind direction from upwelling-favorable to downwelling-favorable conditions occurred during the week prior to the stranding event. Cetaceans are known to track frontal convergences; therefore, they might follow an upwelling front. A change from upwelling-favorable to downwelling-favorable winds would cause the front to move inshore and may explain cetacean movement towards shore. It is important to note that not every switch from upwelling to downwelling-favorable winds causes a mass stranding, so there must be other factors that are involved. This study also found that mass strandings were more likely on beaches that have a gentle slope with a sudden drop in depth close to shore. Some researchers have explained the correlation by suggesting that cetacean sonar does not reflect properly in these areas.