Last updated: July 22, 2021
Article
Elephant Seal Monitoring Season Summary: Winter 2017-2018
Season Overview
- Continuing the trend of yearly population increase, the highest ever number of total elephant seals, 2411, was recorded on January 30th. Last year’s peak number was 1824.
- The season had a late start with the first pup born December 26th. Last year’s first pup was born December 16th.
- Minimal winter storms resulted in very low pup mortality. The highest pup count of the year was 1020, last year’s highest pup count was 726.
- The colony on Drakes Beach is growing and moving farther down the beach, resulting in an expanded closure of the beach.
NPS / Marjorie Cox, NMFS Permit No. 17152-00
NPS / Marjorie Cox, NMFS Permit No. 17152-00
NPS / Sean Pickton, NMFS Permit No. 17152-00
Dynamic Drakes
The elephant seal colony on Drakes Beach is growing in size, and moving farther down the beach. The original colony on Drakes was established on the beach below the overlook and is now expanding down the beach towards the visitor’s center. Concerned about the safety of visitors and seals, the park closed the entire stretch of beach from the cliff directly to the right of the visitor center parking lot to the elephant seal overlook. Researchers speculate that seals are moving from the Point Reyes Headlands colonies into the more protected Drakes Bay
Seasonal Peak Elephant Seal Counts, 2015-2018
NPS / Marjorie Cox, NMFS Permit No. 17152-00
Research Goals
Monitoring the elephant seal population at Point Reyes is hard, but rewarding work. Researcher’s primary goal is to document the actual number of seals in the park, this is achieved by conducting bi-weekly counts over the approximately 3 month breeding season. This year researchers had good luck with the weather, and were able to complete almost of all of the planned surveys. In addition, adult male seals were dye marked at the start of the season, to track their movements around the park and their status within the colony. Flipper tags also play an important role in the park’s elephant seal work. Tags are re-sighted throughout the season, allowing researchers to learn the history of specific animals. New flipper tags are applied to weaned pups in the park, in order to track their movements over the years. A record was set this year with 406 unique animals tagged!
NPS / Sean Pickton, NMFS Permit No. 17152-00
NPS / Sean Pickton, NMFS Permit No. 17152-00
Seasons of the Seal
After the breeding season weaned pups will remain on the beach until April, and at that time the molting cycle for other age-classes will begin. Elephant seals and monk seals go through a “radical” or “catastrophic” molt, and are the only pinniped species to do so. This type of molt not only sheds hair, but also a layer of skin. Catastrophic molts require a lot of energy, and elephant seals will once again fast and remain on the beach for 3-4 weeks until the process finishes.
Preliminary Data
Total Elephant Seal Counts, Winter 2017-2018
Female Elephant Seal Counts, Winter 2017-2018
Elephant Seal Pup Counts, Winter 2017-2018
Weaned Elephant Seal Counts, Winter 2017-2018
Weelky Updates Recap
News This Week
- Cows continue to arrive at all sites
- Steady increase in pup births
- Drakes Beach closure begins
The 2018 elephant seal breeding season continues to ramp up at Point Reyes National Seashore! A closure is in effect at Drakes Beach, as we have seen a marked increase in cows and pups on the beach.
Twins
It is common to observe female elephant seals at the colony with two pups in close proximity. It may appear that the cow has birthed twins, but in fact twin births in elephant seals are extremely rare. No eyewitness accounts have ever been documented of the birth of twins in Northern elephant seals. It is more probable that one of the pups has been abandoned or moved away from it’s actual mother.
Runny Noses
Why do elephant seals seem to have perpetually runny noses? It may seem they have a severe case of the sniffles, but in fact this white fluid around their nostrils is pulmonary surfactant! Surfactant is an important substance for mammal respiratory systems, decreasing surface tension of lung fluid, and allowing for gas exchange. In deep diving pinnipeds, like elephant seals, it serves another function. Immense pressure during deep dives collapses the lungs. Pulmonary surfactant acts as a “non-stick” coating that allows lungs to re-expand as the seals rise to the surface.
News This Week
- Cow and pup numbers increase, especially at the Drakes Beach colony
- First weaned pups of the season seen at Drakes and Point Reyes Headlands colonies
- Last week’s 20+ ft. swell caused pup loss at Point Reyes Headlands
- Drakes Beach closure extended
An explosion of pup births is anticipated in the coming week, as we have a large number of pregnant cows on the beaches. Bulls are asserting their dominance and forming harems, as younger males increasingly get pushed to the outskirts of the colonies.
Drakes Beach Closure Extended
The Drakes Beach closure has been extended due to an increasing number of seals hauling out in proximity to the visitor center. Park staff are concerned for the safety of visitors and seals, and have decided to extend the closure starting January 27th. The original closure began about ½ mile down the beach to the right of the visitors center. The new closure will begin at the start of the cliffs to the right of the visitor center.
Beachmasters
Who is alpha male on Drakes Beach? Looking down from the overlook you may be able to spot the dominant males by the dye mark applied by researchers. Currently we have 3 harems on the section of the beach visible from the overlook. D1 has been alpha since the beginning of the season and is with a large group of females on the far side of the beach. D4 has a smaller harem closer to the overlook. The third harem has an unmarked male as alpha. Dominant males can be identified by their massive size and impressive chest shields. They are usually central in a group of females, although if they have been defending their territory they may be on the outskirts.
Flipping Out
Sand flying through the air propelled by the fore-flipper of a seal, is a common sight at elephant seal colonies. Sand flipping is an important tool in thermoregulation for the seals. Wet sand displaced onto the animal’s body, results in evaporation, reducing the animal’s body temperature. The sand also acts as a sunscreen and a remedy for skin irritation. When conflicts arise, which they often do in a crowded colony, the seals also use sand flipping as a way to redirect stress.
News This Week
-
Possible peak of the season hits, and expected decline of females expected next week.
-
Mating activity has been observed.
-
Drakes Beach closure continues.
High numbers of elephant seals at the park were recorded this week, with 2,441 total seals Tuesday, January 30. While pups are still being born, we are seeing an increased number of weaned pups. As the pups get close to weaning, the females will come into estrus and mate with the males. Mating and the departure of female post weaning, may be observed from the elephant seal overlook.
Radical Re-sights!Researchers at Point Reyes conduct weekly surveys to document tagged animals, allowing for data collection on the movement of individual animals.This week, we had two exciting tag re-sights! A pregnant cow was spotted on Drakes Beach, with a massive healed shark bite on her back. She has a bright green tag in both rear flippers, which means she was tagged at Año Nuevo, but she has been consistently seen in Point Reyes since 2013. Also on Drakes Beach, a nursing cow was spotted with a pink Point Reyes flipper tag. She was tagged as a weaned pup in 2000 at the Headlands colony, and this is the first time she has been spotted since! It is possible this 18 year old cow has recently decided to relocate to the more protected Drakes colony for the breeding season. Elephant seals often return to breed at the beach where they were born, but these two females demonstrate that this is not always the case.
Eggcelent Timing
Pinnipeds (seals and sea lions) employ a reproductive strategy called delayed implantation. This delay allows for the timing of the birth to correlate with favorable environmental conditions, regardless if mating occurs early or late in the breeding season. The total gestation period for northern elephant seals is approximately 11 months. After successful mating, female seals will delay implantation for about 3 ½ months, after which the fertilized egg will implant in the uterus and continue to develop for the next 7 ½ months until birth. Examples of other animals that delay implantation are Ursids (bears) and Mustelids (weasels and otters).
News This Week
- Pupping begins to decline
- Cow departures increasing
- Males are extremely active in their attempts to mate
While a few elephant seal pups were born this week, a large number of pups have been weaned as cows leave the beach. Mating activity is prevalent, and males are keeping busy either defending their harem or trying to sneak into one. D4 and D1 are still holding down alpha positions on Drakes Beach below the overlook.
Stay Cool
Unseasonably warm weather in Point Reyes has the elephant seals desperate to cool off. Researchers have observed changes in their behavior: entire harems are moving to the water’s edge, cows are bringing their pups into the surf zone, and seals are seeking out standing water if they can. Sand flipping is rampant and seals are also extending their flippers, which allows them to release heat.
Clap Back?
The vocalizations of male northern elephant seals, also called ‘clap threats’, are often heard at colonies. Recent research out of UC Santa Cruz emphasizes the importance of these vocalizations in determining if males will engage in physical altercations. Clap threats of individual males have an acoustic signature, distinct for each individual. While alpha males will defend their harem against all subordinate male intruders, lower ranking males use these vocalizations to determine if a fight is worth the energy expenditure. The seals are able to recognize clap threats from individuals they have encountered before, remembering the signature of other seals even from previous years. If the vocalization they recognize is from a seal that dominated them in the past, the seal will avoid a fight they are likely to lose.
News This Week
- Mating activity is prevalent at all colonies
- Cow departures equals increase in weaned pups
- Efforts to tag weaned pups are a top priority
Coincidentally, the height of elephant seal mating occurs during Valentine’s week in Point Reyes! Cows are leaving the beaches in droves, which occurs soon after mating. Weaned pups are left behind and will remain on the beaches for up to 12 weeks. The weaners will form pods, where they will learn together how to function in their environment. Researchers hope to tag upwards of 300 pups this season.
Against the Odds
It’s not easy being alpha male, but it’s even harder for elephant seals to achieve that coveted status. Only 5% percent of males born survive to physical maturity, and less than 1% successfully mate in their lifetime. Not being alpha does not mean that a seal will never breed. Observable on Point Reyes beaches at this time of year are the efforts of subordinate males to get their chance at mating. Subordinate males will lurk on the periphery of the harem, and when the alpha is distracted by mating or fighting off other males, they will have their chance to make their move. Non-alphas will move quickly, albeit sneakily, into the harem. It’s a risky game, as cows are less receptive to non-alpha males. Cows will often put up a noisy fight, attracting the attention of the previously preoccupied alpha, but it’s a risk worth taking.
Milking It
Gaining weight daily is the top priority of elephant seal pups. Elephant seal milk is about 34% fat, and in about 28 days pups can balloon from about 70 lbs. to 300 lbs! However, some pups can exceed 500 lbs. if they are wily enough to become “super weaners”. These extra chunky pups become milk thieves, stealing milk from cows after they have been weaned from their own mother. This is a dangerous strategy as cows are often aggressive to pups not their own. Super weaners are almost always male. The canine teeth of female pups erupt before weaning, but for males this can occur up to 4 weeks after weaning. The lack of teeth makes it easier for males to successfully thieve.
News This Week
- Majority of elephant seal cows have bid farewell to their pups, and departed for the open ocean.
- Very low pup mortality this season means the beaches are filling up with weaned pups.
- Males are desperate to mate, as only a few females are left.
Pup Protectors
As cows leave the beaches of Point Reyes, a marker of their success this season is to leave behind a fat and healthy pup. The mother’s physical condition, and her ability to provide nourishment are of course important factors in successful weaning. However, the female’s behavior and ability to defend her pup are important for her pup’s survival as well. More dominant and aggressive cows are more successful at defending their pups against the bites of other females or males in the harem. Dominance also allows a cow to secure the choicest spot in the harem, often in the center of the group, where she can avoid subordinate males, rising tides, and other disturbances that could harm her pup. Older females are aggressive more frequently, and therefore more likely to hold a higher rank in the harem.
Marvelous Males
Impressive displays of stamina are on display below the Drakes Beach overlook. Alpha males D1 and D4 are still dominating, as they have since the very beginning of breeding season. D4 has been observed aggressively defending his harem against subordinate males. D1 has the largest harem on this stretch of beach, and his presence alone seems enough to keep other males away, but who knows what he’s up to when humans aren’t watching. Another amazing alpha, D2, has been harem master in Gus’ Cove (near Chimney Rock) the entire season, at the height of the season defending a harem of over 150 cows!
News This Week
- Only 79 elephant seal cows remain in Point Reyes as of Feb. 27, down from seasonal peak of 1225.
- Majority of weaned pups appear to be well nourished and healthy.
- Researchers continue flipper tagging pups, and have tagged 397 unique animals so far!
Wonderful Weanlings
Now that the majority of pups born in Point Reyes are without mom, it is time for them to learn how to be an independent seal. However, achieving this independence relies on important social interactions with fellow weaned pups. Pups will practice aggressive behaviors that they will need to be successful adults. Males more frequently display mock aggressive behavior such as neck biting and body slamming, and female pups mimic the “head banter” behavior of adult females. After weaning and molting, pups will begin to move into the water, often following the lead of older pups. In shallow tidal areas weaned pups will practice swimming, foraging behavior, and breath holding. After approximately 5 weeks of swimming practice pups will be excellent divers, and be proficient enough swimmers to head out into open water to find food.
Dominating D1
Researchers were pleased to read the flipper tag of Drakes Beach alpha male D1. The tag was spotted earlier in the season, but as D1 was surrounded by cows and pups it was too difficult to read. We got our chance this past week. The green tag was from Año Nuevo, after reaching out to researchers there we found out that D1 was tagged as a pup ten years ago, and re-sighted once at Año 5 years later. It will be exciting to see if this 10 year old bull returns to Drakes Beach next year!
Elephant Seal Seasonal Monitoring Updates Home
The National Park Service shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data and related graphics are not legal documents and are not intended to be used as such. The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and consistent within the limitations of geospatial data in general and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data; it is not appropriate to use the related graphics as data. The National Park Service gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from an NPS server and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully on computer systems at the National Park Service, no warranty expressed or implied is made regarding the utility of the data on other systems for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. The National Park Service requests that the data user refrain from publishing these data and related graphics and wait until data is available in official, published reports.