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Photoidentification | Social structure
| Foraging behavior | Acoustic behavior | Genetics
Photoidentification
During seven field seasons, 1999-2005 we identified near 300 animals. The ratio of resighted individuals increased between 2002
and 2003 from 26% to 36.4%, while the ratio of new animals identified
has decreased, from 38% in 2002 (n=38) to 17.4% (n=21) in 2003.
The most remarkable findings are the two cases of Photo ID evidence
that shows the animals we met travel in quite wide-range. As it has
known by the studies in eastern North Pacific, we made it for sure
about travels for some 1,000km (1999 and 2002 re-sightings) and over
600 km range in one season (in 2002 re-sightings).
In addition, we casually continuously accumulating ID Photographs
from other areas in western North Pacific including Sakhalin, Kuril
Islands and Japan, and to date, we have not found any single match
between these recognized animals and our identified animals from
Kamchatka yet.
Social structure
We found out that 160 of identified orcas regularly and often occur in Avacha Gulf in summer and make up 87% of all encounters.
All encounters with these orcas took place on the distance no more than 16 km from the shore.
We analysed how often each two of these 160 orcas were encountered in one group. The results suggest that whales usually travel in stable groups, proably representing matrilinear units. According to the results of acoustic analysis, all these groups belong to the same acoustic clan ("Avacha clan").
Besides 160 "usual" orcas we also identified some animals which visited the area 1-3 times a season. We called them "strangers". Groups of "strangers", which were et only once, were excluded from analysis. "Strangers" also traveled in stable groups.
We observed some of the "strangers" together with the "Avacha clan" orcas. During this some of them formed mixed groups and actively interact with the "Avacha clan" orcas, and others did not mix and interact. The latter were named "offshore" because they were usually encountered on the distance 13-30 km from the shore.
All orcas mentioned above correspond in appearance, as well as behavior and acoustic activity, to the fish-eating ecotype of the eastern North Pacific.
Besides this, we also met killer whales similar to the mammal-eating orcas of the eastern North Pacific. These orcas were not encountered together with fish-eating ones.
Foraging behavior We observed several types of foraging behavior: "carousel"
- surrounding and diving in the center of school of fish one after
another, and chaotic diving, when group is foraging within determined
area, either in tight group or in subgroups of 2-5 animals. Observations
of foraging were evenly distributed during the daytime with a little
increase in the period from 11 a.m. to 2 p.m.
Visual observations conducted in 2000-2001 showed that killer whales
from year to year forage in the same regions of Avacha Gulf. In
2002 with the use of theodolite we described these places in geographic
coordinates. No events of aggression or hunting behavior addressed
to marine mammals presented in the gulf (largha seals Phoca largha,
Steller sea lions Eumetopias jubatus, sperm whales Physeter macrocephalus,
minke whales Balanoptera acutorostrata and Dall's porpoises Phocoenoides
dalli) were observed during the study period. We watched non-aggressive
inter-species interaction between killer whales and Dall's porpoises.
We analyzed size of 106 groups observed in Avacha Gulf in 2000-2002.
Groups contained from 1 to 49 animals (mean=9.56), but the usual group
size ranged from 6 to 10 animals, which is was rather similar with
the group size of fish-hunting form (resident type), than of the mammal-hunting
form (transient type) known by the killer whale studies in eastern
North Pacific.
Acoustic behavior Observed killer whale groups proved to be highly vocal, producing
sounds during most of the recordings. These sounds included discrete
and variable calls, whistles and echolocation in different proportions.
We have created the catalog of discrete calls of Kamchatkan orcas.
With the acoustic analysis of vocal repertoires of different killer whale groups,
we revealed 8 resident pods occurring in Avacha Gulf from year to year.
All these pods shared at least one discrete call type, which by definition means that all are members
of the same clan (Ford 1991). We named this clan “Avacha clan”.
We also found several pods which shared no calls with these eight. Their status and relationships are not yet defined.
The dialect of one of them, named “K20 clan”, was also frequently recorded.
Two other groups – “K32” and “offshore” – were recorded more rarely.
In addition, we also sometimes encountered killer whale groups with dialects
that differed from all of those mentioned above. It is known that killer whales
can travel great distances of up to 5500 km (Guerrero-Ruiz et al., 2005); therefore,
these groups may have come from some distance away, crossing Avacha Gulf on their migration.
All groups mentioned above correspond in appearance, as well as behavior and acoustic activity,
to the fish-eating ecotype. Probable mammal-eating killer whales were recorded in Avacha Gulf only once.
Calls of these whales differed from the dialects of all other groups ever recorded in Avacha Gulf,
but were similar to the calls of mammal-eating killer whales from the Pacific coast of North America
(H.Yurk, pers.comm). During the recording we also heard distant (10-15 km) calls of fish-eating whales from
the “Avacha clan”, but these whales showed no visible reaction to them.
Genetics Genetic analysis showed that
most of our fish-eating orcas had SR-haplotype (like Canadian Southern residents and one clan of Alaskan residents).
As a result, we can suppose that in Avacha Gulf region occur at least two separate
killer whale populations. One of them is fish-eating. We have found out that our "usual" whales
have sociobiological features similar with North-American resident
killer whales' populations. They live in large groups, actively vocalize
and show no interest to other marine mammal species. We are not discussing
the estimation of total numbers of killer whales in Kamchatka coastal
waters, because of lack of data, but resident populations throughout
the eastern North Pacific generally number fewer than 300 individuals.
Since Southern Canadian residents now have a status of threatened species (Baird,
1999), we can suppose that capturing of killer whales in Kamchatka
waters will also result in serious decline of their population.
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