Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

Numbers, numbers, numbers!

By | January 25, 2018

swells

Since our last “Pupdate”, the island has suffered it’s first winter storm which introduced nearly 25 foot swells to the shore line!

Unfortunately, these natural wonders had some detrimental effects on the colony. The team stood by in awe as some of the incoming swells swept cows, bulls, and pups alike out of the lower harem on Mirounga Beach. While some of the cows swam by their pups and provided support through the storm, others moved to higher ground as the storm washed their pups out to sea. None the less, the island E-seal population has tripled since our last blog post, which means there are a lot of animals for Team E-seal 8 to be keeping track of! And we bet you’re wondering just how the island biologists stay on top of all the arriving cows and their pups…

Each day, the team heads down to the main colonies to take attendance. This is achieved by looking at each harem and determining which cows and pups remain from the previous day, who departed, and who arrived.  As pups are born and more cows and bulls arrive, the animals shuffle around throughout the day due to various sources of disturbance within the colony, and identifying individuals becomes increasingly difficult from one day to the next. So how exactly do we identify each E-seal? Individual seals are identified a couple different ways.

Some of the animals are tagged in the webbing of their hind flipper with roto tags (much like ear tags on dairy cows), assigning an alpha-numeric number to that individual that can be tracked for years to come.

roto_tag

Other animals are identified by using distinct markings and physical features, such as scars and wounds

.wound extract

As the cows arrive each season, they are assigned a number indicating the order in which they arrived. The first cow is assigned -01, the second -02, the third -03 and so on. These numbers remain with the cows until they’ve weaned their pups and returned to the water in spring. The island biologists take advantage of dry, sunny days to ‘stamp’ these numbers on the cows to allow for easier identification as attendance numbers increase. ‘Stamping’ is a process that involves sponge numbers at the end of a long pole coated with hair dye (a process that is harmless to the animals).

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Here is a small sample of what the team is working with on a daily basis:

harem

Can you identify the individuals in the group photo using the stamp and scar photos provided above?

Respective pups are then accounted for based on visual cues associated with a birth (afterbirth fluids, obvious placenta or umbilical cord etc.), as well as vocal recognition patterns between cows and their offspring. On the days following a birth, maternal relationships are determined by nursing and ‘call and response’ observations. This is, again, a daily challenge as the cows and pups shuffle around, sometimes resulting in sharing, abandoning and adopting pups, but that is a story for another blog post. Stay tuned!

Team Eseal 8

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