MAMMALS

Chris West,
Senior Wildlife Biologist
cwest@yuroktribe.nsn.us

707-482-1822 x 1026

Michael Palermo,
Wildlife Biologist I
mpalermo@yuroktribe.nsn.us

707-482-1822 x 1028
Cell 707-854-3571


Tiana Williams,
Wildlife Technician III

tiana@yuroktribe.nsn.us

707-482-1822 x 1027

Sam Gensaw II,
Tech I

sagensaw@yuroktribe.nsn.us

707-482-1822 x 1025








Yurok Tribe
Klamath Office
190 Klamath Blvd
PO Box 1027
Klamath, CA 95548













Marine Mammals

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Marine mammals are traditionally very important to the Yurok Tribe. Tribe members have known for a long time that whales, usually grey whales (Eschrichtius robustus), enter the Klamath River and frequent local bays. When whales die in the river or wash up fresh on local beaches they are used as an important source of materials, for regalia, tools, and as food. Similarly, since time immemorial, sea lion meat has been used for food, skins have been used for drum heads, and teeth have been used in regalia.

Recently, interest in recovery of California condors (Gymnogyps californianus) on the North Coast has prompted an examination of marine mammals in the region. Population estimates are important to understand how the different species are doing, and if they represent a stable food supply for a large reintroduced avian scavenger such as the condor. Documentation of haul-outs (places where groups of pinnipeds (seals and sea lions) come onto land together) has been started and dead stranded animals on beaches are documented.

A relatively new concern of the current California Condor Recovery Program relates to organochlorine pesticide contamination in marine mammals along the west coast of North America. DDT is the best known of these contaminants, although DDE, a breakdown chemical, is as toxic and more persistent in the environment. Original concerns over DDT related to eggshell thinning in birds, but the toxin also has many effects on the health of mammals (including humans) such as: disrupting the immune system, disrupting the central nervous system, disrupting hormone production, causing endometriosis, and contributing to breast, testicular, and prostate cancers to name just a few. Studies of condor eggshells prior to the widespread use of DDT in the 1940s, found that shells averaged 33% thicker than those during DDT use.

Although DDT has been banned in the United States since 1972, it bioaccumulates (gets more and more concentrated as it moves up the food chain) and binds to fats. These properties allow it to persist in blubber of long-lived marine mammals. Research has shown that historic populations of condors from more northern parts of the range, Monterey Bay and northward, had high portions of their diet comprised of marine resources, likely including marine mammals. Condors released in Big Sur by the Ventana Wildlife Society often feed on seals, sea lions, and whales (Figure 1). Recent evidence of eggshell thinning and high concentrations of DDE in reintroduced condors in Big Sur that feed regularly on pinnipeds have renewed concerns over the potential negative effects this could have on the reintroduced birds ability to breed. Such effects could slow overall progress toward achieving the many goals outlined for California condor recovery. For this reason, examination of organochlorine contamination in marine mammals is important to condor biologists.

Condors feed on a grey whale

Figure 1. California condors feeding on a grey whale in Big Sur, California. Photo courtesy of Ventana Wildlife Society.

Until recently, a data gap existed regarding the examination of organochlorines in marine mammals along the Northern California coast. Filling in this information gap was critical to understanding the current level and geographic extent of this threat to potential reintroduced condor populations.

Figure 2. Total DDTs in Blubber from California sea lions, Del Norte and Humboldt Counties (2009-2012) versus Southern California Bight (1994-2006) (Blasius and Goodmanlowe 2008).

Figure 2. Total DDTs in Blubber from California sea lions, Del Norte and Humboldt Counties (2009-2012) versus Southern California Bight (1994-2006) (Blasius and Goodmanlowe 2008).

The Yurok Tribe’s Wildlife Program biologists have been collecting blubber from dead marine mammals washed up on beaches between Fort Bragg and the Oregon border and testing them for organochlorine contaminants. Many groups including: Redwood National and State Parks, Arcata Fish and Wildlife Office, and researchers from Humboldt State University have helped on this project through information on marine mammal carcass locations, help collecting samples, and with permitting. Results so far seem to indicate that pinnipeds in our region have much less DDT contamination than those tested in Southern California. California sea lions, which travel up and down the entire West Coast of North America, had much lower levels of tested contaminants in Northern California than those tested in Southern California (Figure 2). This is likely because the less time they spent in contaminated Southern California areas and the more time they spent in clean Northern California areas made them both more likely to have low contamination and more likely to eventually die in Northern California. Contamination levels in Pacific harbor seals confirmed the likelihood of this scenario (Figure 3). Pacific harbor seals have much smaller ranges than most other seals and sea lions on our West Coast.

Figure 3. Total DDTs in Blubber from Pacific Harbor Seal, Del Norte & Humboldt Counties (2009-2011) versus Southern CA Bight (1995-2003) (Blasius and Goodmanlowe 2008).

Figure 3. Total DDTs in Blubber from Pacific Harbor Seal, Del Norte & Humboldt Counties (2009-2011) versus Southern CA Bight (1995-2003) (Blasius and Goodmanlowe 2008).

Because of this, contaminant levels in individuals reflect more closely the contaminant levels of the area in which they live. This project is ongoing.

Literature Cited Blasius, M. E., and G. D. Goodmanlowe. 2008. Contaminants still high in top-level carnivores in the Southern California Bight: Levels of DDT and PCBs in resident and transient pinnipeds. Marine Pollution Bulletin 56:1973-1982.

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