Where did the harbor seals GO?

It can be frustrating (and/or alarming) to go to the beach to see the seals and find only empty sand. Where did they go? Have they abandoned Children's Pool? Left La Jolla? Been chased off? One hears such questions regularly.

Truth is, nobody really knows where they go when they leave the beach and Seal Rock area; "out to feed" presumably covers many absences, but is not the whole story. What we do know is that there is nothing unusual about coming and going at a seal haulout.

First off, the seals are still around (we'll try to update this page frequently, so that "still" always will be current). Here are counts for Fall 1999:

(morning counts, LJFS; click for methods)

With few exceptions, these counts were made before 8:00am, and often there are 50+ seals on the beach before 8:00am and none by 9:00. The overall average is indicated by the dashed line. The seals seem to be early risers and hit the surf soon after sunrise. Click for updates.

Part of the variation is seasonal, as shown here:

(monthly maximum counts, from Yochem & Stewart, 1998)

As you can see, counts at the Children's Pool beach tend to be high during the winter and fall during the summer, reaching a low in October/November before climbing again. One possibility is that the warm, sheltered beach is just a little too warm for the seals during the summer. This certainly fits with the daily pattern, above.

Interestingly, counts from nearby Seal Rock show less variation:

(monthly maximum counts, from Yochem & Stewart, 1998)

This is at least consistent with the idea that it sometimes gets too hot on the sand for the seals to be comfortable. Many of us have both AC and heat in our homes; seals have to find comfortable temperatures some other way. For more on how seals use haulouts to regulate temperature (and so their metabolism, and whole energy budget), click here.

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Daily count methods:: These counts were made by trained LJFS volunteers. They include seals on the sand at Children's Pool beach, the ledge of rock along the seawall, and the submarine-shaped rock in the center of the Pool. Seals in the water were not counted. All September counts were by one observer, and October by another (most of the September counts are from about 7:30-8:00, and October between 6:30-7:30). We ensure consistency by minimizing numbers of observers and using inter-observer reliability checks and training. Counts were made from the sidewalk above CPB and/or the seawall, using binoculars as necessary. Each count was done twice, with 3 or more counts done if the first two did not agree with each other. Two of the counts in this graph (9/12 and 9/30) were rough estimates of "over 50"; 9/20 is "roughly 50" and the rest are thought to be accurate to within about 2 seals.
Yochem, P. K. and Stewart, B. S. 1998. Behavioral ecology and demography of seals and sea lions at the Seal Rock Marine Mammal Reserve. Hubbs-Sea World Technical Report No. 98-282.: This study was commissioned by the City of San Diego. While the study's methodology included time-lapse camera monitoring of the beach area 24 hours per day, data presented in the report (and shown here) are of maximum counts made during one or two all-day observation sessions per month. Given the daily variation shown above, it must be remembered that these figures are from small samples (spread over a long period). As with the LJFS counts, the area defined as "CPB" includes the beach, rock along the seawall, and central submarine-shaped rock.

These counts come from ongoing research by UCSD students. Seals are counted at least twice, with additional counts as needed to resolve discrepancies; whenever possible two observers do independent counts to ensure accuracy.

                   # of seals
date     time   on sand/wall rock/   total #
         (AM)     submarine rock     seals

10/7       7:00       100/1/0       101

10/8       7:00        81/0/0        81
           7:15        73/0/0        73
           7:30        71/0/0        71

10/9       7:10        85/2/0        87

10/10      6:30        86/3/2        91
           6:45        86/3/2        91
           7:15        66/3/2        71

10/11      7:15       136/3/0       139
           9:15        15/0/0        15

10/12      7:15        82/3/1        86

10/13      7:15        78/3/1        82

10/14      7:15        76/0/0        76

10/15      7:18       100/5/0       105
           9:00        97/5/0       102

10/16      7:15        72/3/0        75

10/17      7:15        56/1/3        60

10/18      7:19        35/0/1        36
           8:14        19/0/1        20

10/19      6:45        27/2/2        31
           7:20        25/0/0        25
           8:20        18/0/6        24

10/20      7:15        32/1/5        38
           8:00        32/0/8        40

10/21      7:19        46/0/0        46

10/22      7:19        81/0/0        81

10/23      7:12        49/0/0        49

10/24      7:15        45/1/0        46

10/25      7:15        48/1/1        50
           8:00        39/1/0        40

10/26      7:30        84/1/0        85
           8:00        63/1/0        64

10/27      7:17       127/3/2       132

10/28      7:15       100/4/2       106

10/29      7:15        82/0/0        82

10/30      7:00       111/1/1       113
           7:20       114/2/2       118

10/31      6:50        72/2/1        75
           7:15        61/1/1        63

11/1       6:30        62/3/0        65
           7:30        49/0/0        49
           7:45        48/0/2        50
           8:00        40/0/2        42

11/2       6:30        62/0/0        62
            7:15       40/0/0        40

11/3       6:30        56/1/0        57
           7:15        49/0/0        49
           8:00        49/0/0        49

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