Comparison of activity patterns of nutria (Myocastor coypus) between urban pond complexes in Lafayette, Louisiana, USA and Portland, Oregon, USA

Background/Question/Methods

Little is known about nutria (Myocastor coypus) activity patterns in urban systems. Are the nutria activity patterns in urban pond complexes in Lafayette, Louisiana and Portland Oregon different?

Study 1: Lafayette, Louisiana, USA- The nutria zone at Girard Park (the Park) is comprised of a pond, a retention basin and a buffer zone around the edge of these water bodies. The vegetation is almost entirely lawn grass. The park has been continuously occupied by nutria for at least 15 years. Nutria are not fed, but are habituated to the presence of people. Because of the layout of the park direct observations are possible.  In the Lafayette study,hourly observations were made once a month for 24 hours. We noted nutria number, location, size, and activity.

Study 2: Portland, Oregon, USA- Four urban marsh complexes were studied in the lower Taulatin River Watershed. Each site was a restored wetland within a unique tributary. All 4 sites had restricted public access. Study sites ranged from 5.4 to 21.6 ha. In the Portland study, nutria were fitted with radio-telemetry transmitters and released at the site of capture. Activity levels were monitored with centrally placed data loggers every 5 minutes from August-December 2011. The number of animals monitored varied from 28 at the start to 8 at the end of the study.

Results/Conclusions

In Lafayette, peak activity was between 22:00 and 3:00 throughout the year. There was a significant overlap of nutria and human activity between 18:00 and 24:00, and nutria went back into hiding between 03:00 and 04:00, well before human activity picked up in the morning. This pattern did not vary much during the year, although more nutria were seen during the day in the winter than in the summer.

In Portland, in August, nutria exhibited a late night decline in activity starting around midnight with activity picking up again late morning (08:00-10:00). This pattern shifted until in December activity declined between 15:00 and 18:00 hours and did not pick up again until 06:00 and 08:00 hours. The activity pattern was similar at all 4 study sites.

We concluded that activitie patterns differ in the two areas. In Lafayette nutria behavior showed no seasonal shifts in activity pattern while in Portland they did. In Lafayette, nutria patterns could not be directly related to human activity. We are exploring the role that alternative factors might play in the activity patterns.