The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.July 2014
Salish Sea, Pacific Northwest
This is pupping season in the Salish Sea for Harbor Seals. These seals are by far the most common marine mammals hereabouts, and this genetically distinct population does not migrate out of the Salish Sea. Seals were killed in huge numbers during the century before the Marine Mammal Protection Act of 1972. Since then the population increased until the 1990s and has remained stable since then, at or near carrying capacity, in spite of about 2000 baby seals born every year.
On offshore rocks, protected from raccoons, dogs, people and other terrestrial hazards, seals bear their single pups in summer. Seals aren't particularly sociable, but they share haul-out spaces, especially at this time of year. Here's a group of three mom-pup pairs and two big males, sharing the rock with hundreds of gulls on July 22. The pup on the right is considerably smaller, born more recently.
These are wild animals but their high density (about 3 seals/square km) means I see them frequently. I can show you some seal pupping activity from the last couple of months, and share some facts about it.
more below the tangle of bull kelp....
(All photos by me. In Lightbox...click to enlarge)
A mom and her pup form the closest social relationship among Harbor Seals. She mates in summer after weaning her pup, and is pregnant for most of the year. Delayed implantation means the fetus develops over 9-10 months. In the Salish Sea, seals give birth later than along the coast, with most born between late June and early September.
Average delivery time is 4 minutes. Mom can delay delivery if she's feeling threatened, even go into the water and resume later.
Pups are precocious, able to nurse and swim within an hour. In the 4-5 weeks until it's weaned, a pup will more than double in size, and become skilled enough in diving and fishing to take care of itself.
Once we were out in our sailboat and passed by a mom and a newborn pup on July 15. The pics are blurry, as they appeared suddenly, and were a ways off (maximum telephoto and cropped, as all these pics are) (plus we're all in motion!), but the mom has brought her pup out about quarter of a mile from the nearest haul-out island, into deep water. Amazingly precocious. The pup is swimming on its own but it looks like mom swims under it to give pup a rest. I know this pup is just a few days old because it still has a pink umbilicus showing.
Because of the extremely rich milk she provides (50% fat!) the mom will lose a third of her own body weight during nursing. She spends more than half her time fishing to keep up, and hauls out to rest and conserve energy.
On July 27, I watched a group of seals hauled out on a low rock, including a mom-pup pair. The tide was coming in. While the mom napped, well situated, the pup was resting in a spot where the waves were washing over. It got boiled and swept off twice, crawling back on to be near mom, and then gave up. These are a few snaps from that episode. Mom joined pup in the water and they swam off into a kelp bed. An incoming tide is the best fishing time anyway.
My local bay is home to one friendly seal who plays with us in our kayaks. I've written about her before. One day, we saw another seal in the bay too: a mom and a pup. This was July 25, and I wondered whether this was the same pair with the newborn pup I'd seen earlier, but getting a good look at each of the mom's faces (in my other pics), I could see they were not the same individual. Friendly Seal did not interact with the mother and pup at all that we saw. Mom and baby were sleeping in this quiet protected bay. Sometimes mom was awake, sometimes pup, sometimes both, noses above the surface, eyes closed. Mom was so relaxed her tongue draped out. But never sound asleep, more dozing. They always knew where we were.
For a while pup rode on mom's back. They do that when they get tired. Mom doesn't seem to mind sinking a bit more.
Seals are pretty quiet, unlike sea lions. Baby seals do call out for their moms. They sound just like a baby - "maaaaa".
Pups spend a lot of time in the water with their moms, but sometimes they are left ashore while mom power-fishes. Here's a lone pup I saw from the boat. If you look closely, you'll see other seals in the water there. One might be the mom.
The mortality rate of baby seals is much higher than that of adult seals. They are hunted by Bigg's (transient) killer whales and in the fall by Steller sea lions. If they become separated from mom they die of starvation. Human interference is a risk factor. There are diseases and environmental toxins. Entanglement in abandoned fishing gear and drowning. Getting hit by boat propellors. It is inevitable that some seals will not survive, leaving the better-adapted (and luckier) to keep the population numbers stable.
I see dead pups at this time of year. Here's one being scavenged by a Turkey Vulture.
Male Harbor Seals do not live as long as females. They fight and posture during mating season, getting injuries and losing weight. These two males show facial lacerations, but things are peaceful at this moment. Males spend more time hauled out resting too at this time of year.
Since I am a terrestrial creature, most of my sightings of seals are of them peeking above the surface, or on land, where they rest awkwardly, if alertly, like here watching us go by in the boat. Such calm belies their grace and power underwater, their true element.
Here are some sources for further reading about Harbor Seals:
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