Observations of Beaked Whales
of Pico Island, Azores

M. J. Leal¹ , E. Simas², M. Castro³, M. E. Santos⁴

¹Espaço Talassa, Rua do saco, 9930 Lages do Pico, Portugal. rafoto@yahoo.com

²Bairro da NAV, Rua B nº 40, 9580 Vila do Porto, Sta Maria, Azores, Portugal.

³CCMAR, Universidade do Algarve, 8000 Faro, Portugal

⁴Instituto Superior de Psicologia Aplicada, Lisboa, Portugal

Introduction: The Azores islands make op a volcanic archipelago situated in the mid Atlântic ocean betweem 37º - 40º N and 25º - 31º W, with its nine main islands spread throughout 2352Km² about 900 miles off the coast of Portugal.

The beaked whales are one of the least known families of mammals and, due to their preference for oceanic habitats and generaly boat shy behaviour, it is likely to remain this way in the near future. Several species of beaked wales , mostly of the genus mesoplodon have yet to be seen alive and it is unclear whether all species are already known to science ( MacLeod, 2000).

Four species ok Ziphiids ( Hyperoodon apullatus, Mesoplodon bidens, Mesoplodon europaeus and Ziphius cavirostris), have been recorded in the waters of Azores (see Reiner, 1990; Reiner et al., 1993), but almost all the available information comes from occasional sightings or stranded animals.

The south coast of Pico island was once one of the most important areas for land- based whaling operations. The old watchtowers situated on strategic spots on land used in whaling times are nowadays used by whale watching operators. Last summer we used one of this watchtowers to observe and obtain data on the movements and behaviour of these animals.

Methods: The study area was the south coast of Pico island and the watchtower we used was located at 38º 23’ 094" N, 28º 14’ 418" W, at an altitude of 75m. the distance covered was almost 20Nm offshore.

Observations started early June 2000 and ended in the beginning of October, and completed 18 weeks with some interuptions. The observation effort was 572 hours distributed in periods from 09:00 h to 13:00 h and from 14:oo h to 18:oo h. 10 x 50 Olimpus binoculars were used and with the help of an experienced look- out from the whaling times, we took records of all the sightings.

Records frrom these sightings included species or genus identity, position and depth, hour, sea state (Beaufort scale), wind direction, visibility, swimming direction, size of groups, presence of calves and predominant activity.

Observaions were conducted in concern with the whale watching boat crews, who wee able to confirm a part of the data obtained from shore. In all cases, care was taken to reduce the possibility that the same group was scored in consecutive records.

Results: This observation effort resulted in 147 sightins of ziphiids, of with 12 were bottlenose whales. Of the 135 sightings of Mesolodon groups, 12 were further identified by closer observation in whale watching boats as Sowerby’s beaked whales ( M. bidens).

Positions of sightings for both groups are presentated in fig. 3 and 4. This occurred in all directions covered from he watcthtower.

Average group size was 4,3 (S. d.= 2,4), for Mesoplodon and 5,3 for Hyperoodon ( see group size distribution in Fig. 5 and 6).

For Mesoplodon, a weak negative correlation was found between group size and distance from shore ( highly related also to depth): Sperman correlation coeficient rs= - o.25, p< 0.004, N= 135.

No calves were observed in any of the groups. Other data , concerning montly variation in sightings, morning- aftenoon variation in sightings, swimming direction and predominant activities are presented in Figs. 7,8,9,10,11 and 12.

Discussion: This study provides some useful informatin concerning the occurrence of beaked and botlenose whales off Pico island during summer mounths. It shows that a gpood deal of data may be obtained in shore-based observations, although clearly these could be much improved by permanent communication between the watchtower and the boat crews. A consistent general swimming direction was not detected; our data therefore does not suggests that Ziphiid movements near Pico island during ths time of the year are part of any particular migratory pattern. Group size showed a slight tendency to increase with proximity to shore, whith might be related to feding acivities. The fact that no calves were spotted does not allow us t o contribute to the identification of any calving season or peak.

Aknowledgements: We would like to thank Espaço Talassa and all the team that works there for the suport in this study.

Thanks are due to Sr. João, Sr. Sidónio and Sr. Antero for teaching us so much.

Prof. Joaquim Lu's for providing the Pico Island map.

References

MacLeod, C. D. 2000. Species recognition as a possible function for variations in position and shape of the sexually dimorphic tusks of Mesoplodon whales. Evolution 54 (6): 2171- 2173.

Reiner, F. 1990. Records of marine mammals of the Azores islands. Garcia da Orta, Série de Zoologia, 15(2): 21- 36.

Reiner, F. , Gonçalves, J. M. & Santos, R. S. 1993. Two new records of Ziphiidae (Cetacea) for the Azores islands with an updated checklit of cetacean species. Arquipélago ( Life and Marine Sciences), 11A: 113- 118.