Connectedness and synergistic interactions between different threats
In December 2014, the Southern Resident orca Rhapsody (J32) was found dead carrying a near full-term fetus. The loss of a reproductive female and her calf was a hard hit to the Southern Resident population. Preliminary results from her necropsy showed that she was malnourished and had a very thin blubber layer – essentially, she and her calf were starving, but the problem was even worse than that. When a whale is not eating enough, they start to metabolize their blubber layer and those human-caused chemical toxins that had been stored in their blubber are then released into the blood stream. Pregnant and nursing mothers, and new babies, are especially vulnerable to these effects. Toxins that had been accumulated in the mother’s body up to that point are transferred to the calf. This may have been a contributing factor in the death of Rhapsody and her calf, and this toxin offloading process is especially problematic for first-time or young mothers, like J32.
The decline in the Southern Resident population is a product of many different interacting factors. Over the past three weeks we have looked at the major threats: low food availability, chemical contamination, and vessel impacts. Each of these alone is harmful to whales, but the synergistic interaction of multiple threats together spells disaster for the population, unless something changes very soon.
For example, boat noise drowns out echolocation and communication between individual whales, making foraging difficult in a situation where food is already scarce to begin with. This leads to malnutrition, which exacerbates the effects of chemical contamination depressing the immune system. Lots of boat traffic in urban areas disrupts their natural behavior, and sick or underfed whales don’t have energy to spare for avoiding boats or making louder calls. Changing ocean chemistry (due to increased carbon emissions) makes sound travel farther, so boats farther away have more impact. Aside from these main threats, there are other significant concerns, like an already small population size, which carries its own inherent risks, or a potential oil spill in the Salish Sea where they would be incredibly vulnerable. Recently, the National Oceanic and Atmospheric Administration (NOAA) authorized an increased use of SONAR within the Navy’s Pacific Training and Testing range on the outer coast of Washington, nearly doubling the expected number of harassment incidents for marine mammals. And, of course, climate change is a growing threat to their food resources.
Demographics are not on their side, either. Live-take for marine parks removed about 50 whales from the population (favoring juveniles), effectively stealing an entire generation from the Southern Residents. There are some matrilines that have no living females of reproductive age, which are going to die out over time as their members age, to such an extent that the only viable Southern Resident pod that could potentially recover is J pod. The birth of nine new calves since December 2014 (eight surviving) has received significant media attention, and has been assumed by many to be a promising sign of recovery for the population. However, researchers who have spent their careers with the Southern Residents are not so confident. Their first concern is whether these calves will live to reproduce. Before 2015, Scarlet (J50, born Dec. ’14) was the only calf to survive since 2012. Beyond that, at least four of these new calves from 2015 are male. While their arrival is heartening, females contribute much more to long term recovery for the community.
While lack of food is the primary factor driving Southern Residents to extinction, external threats from every angle, plus internal demographic issues, only make it harder for the population to remain stable, let alone grow. In a 2014 interview, Howard Garrett, co-director of Orca Network put it this way: “The absence of any surviving calves for two and a half years is like watching an entire cultural community of orcas fall slowly off a cliff… It’s past time for debating about uncertainty.” **Later this week, we will share our “Ask an Expert” session with Howard, discussing the current plight of the Southern Residents and what they need to recover.
NOAA’s 2008 recovery plan aims to increase population size by 2% per year over 28 years, but so far we have not seen any sure signs of recovery, and present trends could eliminate all three pods in a matter of decades unless something changes soon. Huge shortages of salmon are the most urgent issue, and an increase in critical habitat can help address the issue of adequate prey levels, along with other measures. Toxin exposure depresses their immune system over time, and daily stress from low feeding success and boat noise also contributes to poor health. Critical habitat is a powerful leverage point to address multiple issues at once, by making their habitat more able to support maintenance and eventual growth of their population.
Help us address these threats by protecting their home – sign our letter to the National Marine Fisheries Service urging quick action to revise and expand critical habitat for the Southern Residents.
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