Do river otters encounter birds
at the marsh?

Introduction
North American river otters (Lontra canadensis) are notorious fish predators

… but they also take other prey when
readily available (Lariviere & Walton 1998).

Could a super-abundance of birds
attract otters to the Arcata marsh? 
 

The HSU Wildlife Techniques class 
launched a study to determine:

  • the importance of birds in the otters’ diet
  • whether otters visit the marsh when many birds are present
 

Methods
  • We observed birds, tides and otters at Klopp Lake for 18 days in October 2001.
  • Otter diet was determined by scat analysis. 
  • Otter visits were detected from scats, tracks and sightings.

 
 

Results (birds & tides)
 
Thousands of waterbirds came to Klopp Lake 
when adjacent mudflats were 
covered at high tide.

 
 
 
Otters could encounter many more 
birds at higher tides.

 
 

Results (otter diet)
 
Five of 21 scats had bird remains, otherwise otters ate
fish (9), aquatic insects (9) and crustaceans (4).

 
 

Results (otters & tides)
Up to 4 otters visited the marsh on 9 of 18 nights. 
They visited on nights with higher tides 
during dawn and dusk periods.

 

Discussion & Conclusions
  • Many birds rest and forage at the marsh in the day and at night when otters are active.
  • In Kruuk’s (1995) detailed study at a different coastal site, otters were active when fish prey were inactive and most vulnerable. 
  • Otters may travel to the marsh when birds are most abundant.
  • However, few birds were taken.
  • Other marsh prey were favored by otters.

Literature Cited
Kruuk, H. 1995. Wild otters. Predation and populations.
     Oxford University Press. Oxford, UK.

Lariviere, S., and L.R. Walton. 1998. Lontra canadensis.
     In C.E. Rebar et al. editors. Mammalian Species, No. 587.
     American Society of Mammalogists, New York, New York
 

 
Reference to this poster: Black, J.M. 2001. Do river otters encounter birds at the marsh? http://humboldt.edu/~jmb7002/stud/otter/09curr/poster1.html (your date of viewing). Students: Sarah Adams, Monet Belltawn, Thea Benson, Lauren Blaschke, Julia Boland, Jesse Conklin, Pam Conn, Sean Connelly, Helayna Cooney, Kevin Crouch, Laura Davies, Valerie Eurs, Pia Gabriel, Wes Ghormley, Terry Glab, Adriana Guzman, Andrew Hagen, Marcie Lima, Justin McMahon, Wendy Mellberg, Sean Munson, Angela Nelson, Josh Nowland, Chris Rall, Carrie Ransom, Weylan Shaw, Morgan Strachan, Joy Taylor, Maria Topper, Gene Weckman, Trista Welsh 
                                       an HSU Wildlife publication