Investigation Of Common Eider Mortailty Events At Cape Cod Ellis, Courchesne Tufts Svm
Investigation of Common Eider Mortality Events at Cape Cod Julie C. Ellis, PhD Sarah Courchesne, DVM Seabird Ecological Assessment Network (SEANET) Cummings School of Veterinary Medicine at Tufts University North Grafton, MA
SEANET: Beached Bird Surveys & Necropsies Volunteers (Citizen Scientists) Walk same area of a beach 1-2 times per month Record : Conditions data Beached birds (beached birds/km) Live birds “ Fresh” carcasses collected for necropsy
SEANET: Goals <ul><li>Goals </li></ul><ul><li>Establish a baseline for temporal and spatial deposition of seabird carcasses in order to detect unusual events (e.g. oil spills, diseases) </li></ul><ul><li>Work with the public to research and monitor seabird populations, and to contribute to conservation of the larger marine ecosystem </li></ul>Seabirds are sentinels for the marine environment because they spend some to all or their lives on the ocean
Common Eiders Common Eider ( Somateria mollissima ) Largest duck in the Northern Hemisphere! Breeds in eastern North America, on islands along Labrador, Newfoundland, Quebec (eastern), Nova Scotia, and Maine (small pops in NH, MA) Nest in large colonies on islands Populations from Canada and Maine overwinter at Cape Cod in large numbers (especially in the Nantucket Shoals area)
Location and History of Die-off Events Great Island Jeremy Point Nantucket Martha’s Vineyard Since 1980’s (at least)
Recent Events: A Timeline FEB - MARCH 2006: males OCT 2006: males JULY - AUGUST 2007 *Mostly Adult Females OCT 2007: males More Frequent?
Martha’s Vineyard and Nantucket Island ~300 Common Eiders found dead or dying on beach Birds still alive showed non-specific signs: lethargy, dehydration, weakness None survived rehabilitation COEI Mortality Events at Cape Cod: Feb – March 2006
COEI Mortality Events at Cape Cod: Feb - March 2006 Necropsy findings (cont): 8 out of 9 emaciated, 1 out of 9 thin 8 out of 9 had varying degrees of acanthocephalan parasites (moderate to severe infestations)
Profilicollis botulus (acanthocephalan) infestations Thorny head used to attach to host’s intestinal wall; nutrients absorbed through worm’s body wall
How P. botulus could kill eiders <ul><li>Steal enough nutrients from the host that the host starves </li></ul><ul><li>Plug up the intestine </li></ul><ul><li>Perforate the intestine with the thorny head and allow intestinal contents to escape out into the body (sepsis) </li></ul><ul><li>Leave so many scars in the intestine that there is no longer any surface area for nutrient absorption (malabsorption) </li></ul>
Die-off: Wellfleet Bay, October 2007 <ul><li>14 necropsies performed on birds collected at Jeremy Point </li></ul><ul><li>Demographics: 11 adult males, 1 adult female, 2 immature males (die-off appeared to affect mainly adult males) </li></ul><ul><li>Body Condition: 4 in good body condition, 6 in thin body condition, 4 emaciated </li></ul>
Necropsy Findings <ul><li>One bird had died of gunshot wound </li></ul><ul><li>>90% of birds in fair to good body condition showed pectoral muscle atrophy (indicates recent molting) </li></ul><ul><li>11 of 14 birds had lesions in the digestive system. Most common: </li></ul><ul><li>Pus and scarring on internal surface of esophagus/stomach (see photo) </li></ul><ul><li>Hemorrhage in esophagus, stomach, intestine (next slide) </li></ul>
Necropsy Findings <ul><li>All but one bird had acanthocephalans (ranged from 4 to 267 worms) </li></ul><ul><li>No apparent relationship between parasite load and degree of intestinal inflammation </li></ul><ul><li>One bird died of intestinal perforation by an acanthocephalan </li></ul><ul><li>One bird died of an intestinal perforation (unknown cause) but had no acanthocephalans </li></ul>
Conclusions From 2007 Die-off <ul><li>Scattered liver lesions and hemorrhage in intestinal tract point to a viral cause (NWHS investigating) </li></ul><ul><li>Birds did not starve to death (not universally thin as in previous die-offs) </li></ul><ul><li>Acanthocephalans typically present, but do not appear to be causing big problems </li></ul><ul><li>Most birds had recently been stressed (by molting) and may have been more susceptible to disease </li></ul>
Comparison with eiders shot by hunters <ul><li>8 eider (5 adult males, 1 immature male, 2 adult females) shot in November 2007 at Great Island in Wellfleet </li></ul><ul><li>50% were thin, 50% in good body condition </li></ul><ul><li>3/8 birds had no lesions (aside from gunshot wounds) </li></ul><ul><li>Remaining 5 birds had varying degrees of lesions in digestive tract (similar to die-off birds) </li></ul>
Acanthocephalans in shot birds <ul><li>All shot birds had acanthocephalan infestations </li></ul><ul><li>Parasite number ranged from 8 worms to 426 worms (more than in any of the die-off birds!) </li></ul><ul><li>The parasites were NOT associated with any significant lesions or disease </li></ul><ul><li>Higher parasite loads were not associated with decreased body condition </li></ul>
Significance of findings in shot birds If birds that appear healthy (outwardly) have many of the same lesions as the die-off birds… … either the lesions are a red herring and have nothing to do with the cause of the die-off… … or the lesions represent a disease that many eiders may carry but that only sickens and kills birds that are stressed in some way.
Next steps: Histopathology Contaminants testing Dietary analysis Population studies Beached Bird Surveys Virology Cyanotoxins?
Acknowledgements Jack Renfrew (Ducks Unlimited) Susannah Corona (New England Aquarium) Marc Siegel, KC Horigan, Nadia Stegeman, Emily Christiansen (Tufts vet students) Mark Pokras (Tufts) Michael Moore & Andrea Bogomolni (WHOI) Katie Touhey (CCSN) Becky Harris (Mass Audubon) Mark Jankowski (USGS) Hon Ip (USGS) Funding : NOAA (Oceans and Human Health Initiative) Bernice Barbour Foundation