Point Lobos State Reserve Otter Survey
Monthly land-based standardized surveys of southern sea otters (Enhydra lutris nereis) have been conducted by experienced volunteer docents in Point Lobos State Reserve since 1989. These data are then compiled by the U.S. Geological Survey (USGS) with other otter survey data ranging from Santa Barbara to Half Moon Bay.
The surveys record numbers of independent otters and pups observed, location and behavior. Results are used as an indicator of the population trend of California sea otters in this area. The primary purposes of these surveys have been to identify and illustrate changes in the local otter population for Point Lobos Reserve visitors and to provide this information to the USGS.
Summary to DateThe Point Lobos surveys have been used to generate images to illustrate the changes in local otter sightings for visitors to the State Reserve. The program has also been very successful in contributing to the pool of otter population monitoring information gathered by the USGS.
Data indicate a general decrease in otter sightings over the last 15 years at Pt. Lobos. There was a decrease in both independent otter and pup sightings. Typically the total count of adults and juveniles peaks during mid-summer which is towards the end of the pupping season (Figure 1).
The relative abundance of pups generally exceeds the relative abundance of independent adult otters from February to July and peaks in May (Figure 2). This peak coincides with the January to March pupping season.
The Pt. Lobos otter program is working with SIMoN to digitize historic data to be able to develop summaries showing otter densities and abundance over the last fifteen years. See the PDF link below for an example density map.
- Annual totals of monthly sightings of California sea otters indicate an general decrease in the local otter population at Point Lobos State Reserve.
- The number of otter sightings at Point Lobos typically peaks in June for all otters (independents and pups).
- The high relative abundance of pups from late winter to early summer is consistent with expectations from the known pupping season.
- Age structure
Study MethodsMonthly land-based surveys of southern sea otters have been conducted at Point Lobos State Reserve since August, 1981 although records are sparse for 1981 and 1982. The survey is a collaborative effort, and in the late spring and early fall the figures are sent to the U.S. Geological Survey to be compiled with figures for the over-all range (from Santa Barbara to Half Moon Bay).
The survey records the total number of otters observed and a break-down of the number of adults and pups with the goal of assembling figures for yearly comparisons. Charts and graphs are made up primarily for the benefit of our many visitors as they explain in a simplified form the increase or decrease of our local otter population through the years, a subject that is of great interest to most visitors. Beyond the charts and for further information, we have notebooks containing the maps with detailed positioning of the otters and what activity they are doing, i.e. feeding, resting, grooming, swimming, mating, etc.
The observers are volunteer docents at Point Lobos State Reserve, most of which do this activity on a regular basis so are familiar with the system. Data compilation has been done for us by David Covel. Dione Dawson originally entered data into the system developed by SIMoN. After her passing, Lynne McCammon has been in charge of entering data from the paper data sheets into the SIMoN database.
The docents are divided into two groups: one to walk the North Shore beginning at Cypress Cove and continuing to the Northern Boundary and the other to walk the South Shore from Headland Cove to Gibson Beach. This covers the entire Reserve from land. Each otter must be observed by a minimum of two docents in order to be counted and binoculars, spotting scopes and the Questar are used. One docent in each group is in charge of marking the maps provided by the Geological Survey with whatever activity is seen and accompanying comments. This monthly activity takes about four hours and is very thorough.
Figures and Images
Figure 1. Yearly totals of sea otters observed at Point Lobos by docents from 1990 to 2012. The number of otters is further subdivided in each vertical bar by the following categories: small pups (green), large pups (orange), adults with a pup (brown), and adults (blue).
Figure 2. Number of sea otter sightings during each month in 2011 at Point Lobos. Data were gathered by docent volunteers.
Figure 3. Pt. Lobos docent volunteers conducting a monthly otter count.
Figure 4. Pt. Lobos State Reserve is a very scenic area.
- July 2004 otter densityJuly 2004 otter density map developed by SIMoN.