An Introduction to Bigg's, or Transient, Killer Whales

Sunday, March 1, 2015

Photo of new calf T085D by Howie Tom

 

Bigg’s, or Transient, Killer Whales might inhabit the same waters of the Salish Sea as our endangered Southern Resident Killer Whales, but that is often where the similarities end between the two subspecies.

 

According to National Marine Fisheries Services (NMFS):

 

Bigg's (Transient) Killer Whales occur throughout the eastern North Pacific, and have primarily been studied in coastal waters. Their geographic range overlaps that of the resident and offshore killer whales. The dorsal fin of transient whales tends to be straighter at the tip than those of resident and offshore whales.7 Saddle patch pigmentation of transient killer whales is restricted to two patterns, and the large areas of black color don't mix into the white of the saddle patch that is seen in resident and offshore types. Transient type whales are often found in long-term stable social units of less than 10 whales, smaller than resident social groups. Transient killer whales feed nearly exclusively on other marine mammals.

 

Bigg's (Transient) killer whale populations in the eastern North Pacific feed on marine mammals, such as (in order of frequency of observation):

• harbor seals

• Dall's porpoises

• harbor porpoise

• California sea lions

• gray whale calves

• Steller sea lions

• elephant seals

• minke whales

• various other species of pinnipeds and cetaceans

 

There has been in increase in sightings of transients in recent years, but the increase doesn't necessarily mean an increase in population.  

 

According to Josh McInnes, Marine Biologist at University of Victoria in BC and founder of The Transient Killer Whale Research Project,

 

The increase in sightings can be contributed to two different scenarios. 

1. Due to lack of sightings of southern residents, the whale watch and marine community         focuses on other species. 

2. An increase in their main prey, harbor seals. 

 

“One misconception given is that we are seeing more transients in the Salish Sea. That is incorrect. We are seeing more of the same pods visiting and using the area," says McInnes.

 

The increase in sightings is thought to be due to more awareness and reporting from the general public and from whale watching companies.  

 

The bar graph below shows all known pods that have visited the area in the past two years, and shows the pods according to months. The largest bars represent April, August and September. August and September go hand in hand with the harbor seal pupping season.

 

 

In 2013, The Transient Killer Whale Research Project had a total of 213 sightings. For 2014 they had 263 sightings. Each sighting is separated by a 24 hour period unless a pod meets up with another pod or splits up. That becomes a new sightings.

 

 

Transients are sighted year around, but have seasonal peaks similar to residents. Often from July to September during harbor seal pupping season are the highest sighting concentrations. The search has been extended out to the Sunshine Coast, where different groups of transient that are rarely sighted in the Salish Sea have been found.  McInnes has focused in two different areas and has noticed that different groups prefer certain areas.

 

A few sources have said that numerous California transients have been sighted in the Salish Sea and that these sightings are increasing, but McInnes doesn’t believe that to be true.  He believes that these animals most likely have been visiting these waters for years and being not frequently sighted makes it difficult to ID.

 

The transient population is holding steady, but they face some of the same threats as our residents.  We will explore these threats in further detail in part two of the series.

We will explore California transients and their part in transient research in BC in part three of the series.

 

Transients have been tagged by NOAA and Cascadia Research, however patterns were wide ranging and not predictable.

 

If you see transients in the Salish Sea, contact Josh at jmcinnes@uvic.ca

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