By counting dead seabirds and marine mammals, we are able to document mortality factors (causes of death) for these marine animals. This gives us important information about animals that are often difficult to study because they inhabit the ocean (a difficult place to work) and range over large areas. Some mortality factors may be due to human activities and if we know how many animals are being killed, we can determine if it is a serious threat and then alert management agencies to take appropriate actions.

With BeachCOMBER surveys, we can quantify the relative impacts of different mortality factors. For example, in 1997, many more common murres were found washed up on beaches in the sanctuary than would be expect from just natural causes. Because we were able to quantify the deposition of murres in a standardized manner, we were able to identify an unusual mortality factor, in this case an increase in gill net fishing in southern Monterey Bay which was catching murres in their nets. During the following winter, we also found higher deposition of murres related to an oil spill, the Point Reyes Tarball Event.

BeachCOMBERS data are useful to several groups of people:

  • Resource managers, such as California Department of Fish and Wildlife (CDFW), U.S. Fish and Wildlife Service (USFWS), and National Marine Fisheries Service (NMFS), who are tracking changes in marine bird and mammal populations. For example:

    • Southern sea otter (Enhydra lutris nereis) carcasses were encountered frequently during April – September 1998, January – May 1999, and June – August 2000. Timely reporting of sea otter carcasses benefited CDFW and other researchers interested in identifying and quantifying specific mortality factors for this endangered species.

    • BeachCOMBERS were asked to assume the role of beach assessment and wildlife capture during the mystery spill of October 1997.
    • BeachCOMBERS report banded birds and tagged marine mammals for the USFWS, Point Blue (formerly Point Reyes Bird Observatory), CDFW, and NMFS. Some birds found on beaches of Monterey Bay were initially tagged as far away as Hawaii.

  • Scientists use BeachCOMBERS data to understand harmful algal blooms (e.g., domoic acid), document oiled wildlife, and understand movements and genetics of migratory species;

    • BeachCOMBERS provided some of the first data regarding the impacts of harmful algal blooms and domoic acid toxicity on seabirds and marine mammals (Gulland 2000, Scholin et al. 2000).

  • Teachers and educators use BeachCOMBERS data to teach students methods of conducting science, identifying marine organisms and how to examine or analyze survey data. BeachCOMBERS participate in local community events, educating the public about marine birds and mammals.

    • Volunteers actively interact with recreational beach visitors during each monthly survey, educating them about the BeachCOMBERS program and the Montery Bay National Marine Sanctuary (MBNMS).

    • An annual summary of the activities of the BeachCOMBERS program has been presented in Ecosystem Observations (Benson, et al. 1998, Benson 1999, 2000, Nevins & Harvey 2002) and in the Volunteer Monitor (Ely 2002).

This is the main objective of the BeachCOMBERS project, to document the average trend in deposition rate (number per kilometer surveyed). The deposition rate is dependent upon many factors including wind, swell, tide, the orientation the beach, beach width, and time of year.

The time of year has a big influence on the number of birds and mammals washing in on beaches. During the winter, November – February, deposition of seabirds is low (1-2 per km) due to beach scour and lower densities of birds found nearshore. The number of beached birds (3-6 birds per km) increases during spring and summer with increased numbers of migrating birds and less scour of the beaches. In addition, birds breeding in the spring and summer may experience high mortality rates if food supplies are low or beyond their typical foraging range. The appearance of many malnourished, young bird carcasses has occurred repeatedly in the last two decades.

Fewer marine mammals than seabirds wash up on beaches; an average of less than 1 mammal per km comes in each month. When we have recorded an increase in the deposition rate of marine mammals, we have found it to be associated with a harmful algal bloom (a.k.a. red tide, domoic acid) or starvation due to the El Niño phenomenon, which can reduce the availability of prey.

Rarely. Our ability to determine cause of death is limited by the “freshness” of the carcass. Ideally, we want to examine animals when they first wash in and haven’t been scavenged by turkey vultures, coyotes, or gulls. More often, the carcass is old, dried, scavenged and difficult to identify. In these cases, we still might be able to determine if the animal died of starvation (very thin), entanglement (fishing line or net), or from oil contamination. When we get a fresh one, we use the expertise of biologists and veterinarian pathologists from the Department of Fish and Wildlife, Santa Cruz, Marine Wildlife Veterinary Care and Research Center (CDFW-MWVCRC). The biologists and pathologist will conduct a complete necropsy and test for bacterial, fungal, and viral diseases. They also can x-ray the carcass to look for fragments of bullets or shark teeth.

There are both natural and un-natural mortality factors. The natural causes of death for seabirds and marine mammals are starvation, disease, and predation (e.g., shark bite). Unnatural causes of death are oil spills, entanglement in fishing line or nets, plastic ingestion, boat strike, gun shot, and other human-related causes.

Oil spills kill greater numbers of seabirds than mammals because oil affects their ability to keep warm. Seabirds depend upon their feathers as insulation and get hypothermic (lose body heat quickly) when oiled. Diving birds, such as murres, loons, and grebes, are particularly vulnerable to oil spills because they cannot walk well on land and stay at sea.

Pelicans and gulls that are fed by humans get very tame to people on wharfs and fishing piers and often get tangled in fishing lines. Seabirds and mammals also may be attracted to fish lures, thinking they are fish. Surface feeding seabirds such as albatross and shearwaters mistake plastic for food and consume these unnatural items.

Marine mammals, particularly slow-moving large whales and sea turtles, are often hit by speeding boats. Fishing gear or other trash line that has been cast overboard can be a potential hazard to smaller marine mammals, such as dolphins, porpoises, seals and sea lions.

Coastal Ocean Mammal / Bird Education and Research Surveys (BeachCOMBERS) began in May 1997. This is a collaborative project among staff at Monterey Bay National Marine Sanctuary, California Department of Fish and Wildlife, US Fish and Wildlife Service, and Moss Landing Marine Laboratories. Since the project’s inception, the surveys have been conducted monthly on beaches in Monterey Bay and expanded south into Cambria and San Luis Obispo (~30 beaches). In 2012, the Southern Chapter of the BeachCOMBERS program began and 13 more beaches were added to the monthly surveys. In 2022, the San Diego Chapter of the BeachCOMBERS program began and 6 more beaches were added to the monthly surveys.

Dead seabirds and marine mammals on the beach are part of the natural nutrient cycling on the beach. Beach flies and sand hoppers, which feed on carcasses, are important prey for other animals, such as sanderlings, snowy plovers, and other shorebirds. Scavenging animals such as coyotes, turkey vultures, gulls, and shore crabs also eat these dead animals.

Sometimes BeachCOMBERS will remove animals from the beach if they are of special scientific value (e.g., rare Beaked Whale, endangered species) or oiled.

If animals are cleaned from the beach between surveys, we cannot know if we are getting an accurate count of the deposition. So, we leave animals on the beach and mark them by clipping a toe (or tying a piece of jute twine on marine mammals) to learn how long a carcass will stay on the beach. This is important for documenting the extent of mortality events, and getting a good estimate of decomposition rate. This information also has been useful to resource managers who are trying to calculate how many animals were killed in an oil spill, so they can correct for the number that may have been scavenged or lost at sea.