Wednesday, March 14, 2012

A Weaner's World

A young Northern elephant seal’s life is difficult from the start. At the very moment a pup emerges from the comfort of the mother’s womb, it is greeted by a harsh and violent world. Other mothers may threaten the newborn, often with their teeth, if it wanders or wobbles too close. A neighboring cow might even attack a pup as it is being born.                                  
A neighbor cow bites a newborn

This defensive strategy may protect a cow’s precious milk from being stolen by other wayward pups. Despite being fiercely protected by its own mom, the new pup can hardly escape the males that barrel through the colony in order to chase off intruders or mount the cows in a show of dominance. Often, the new weak pup can be crushed by a two-ton male that it didn’t even see coming. 
MC Hammer with large pup that he had just killed

Sometimes, a pup will become separated from its mother during a scuffle between cows or adult males. It’ll wander around, desperately calling to its mom while other cows snap at it with their sharp teeth. Occasionally, the mother will find the pup and they will be happily reunited. At other times, a lost pup’s mother will abandon it altogether for a variety of different reasons. Because other nursing cows will viciously chase the pup away, it will often end up starving to death. Sometimes the abandoned pup may die faster from wounds inflicted by aggressive adults since it has no mother to protect it. The luckier pups will nurse from their mothers for an average of 28 days before they are weaned and are left alone on the beach. We affectionately call them “weaners.”
Mothers squabble over pups and territory

On rare occasions, however, an abandoned pup might find a surrogate mom who will let it nurse along with her own baby. Despite finding a source of life-giving milk, the adopted pup will have to fight really hard for its share, since the cow’s biological offspring will often be bigger, healthier, and greedier. Sometimes the adopted pup will gain enough weight to make it to weaning, although it often will be smaller than his adoptive sibling. We saw one such case on the island this year, when a tiny female pup abandoned several days after birth found a replacement mother, Lodi, to nurse her. This feisty little creature, was nicknamed “Little 26” (after the number that Lodi and her own pup were bleached with to keep track of them), and she completely won our hearts. 
Little 26 (left) nursing along with her adoptive brother

She was still tiny when Lodi finally left, about half the size of her adoptive brother, “Big 26.” Nevertheless, the tiny weanling found a group of other weaner friends to play with and snuggle up to in order to stay warm. Like the other weaners, she molted her black fuzzy lanugo (natal pup fur) to reveal a silvery weaner coat. She moved all around Sand Flat and had an immense amount of energy despite being so thin that she was basically skin and bones. 
Little 26 (right) with friends

Deep down we all knew that she wouldn’t make it without the blubber reserves that weaners use to provide nourishment and hydration while they learn how to swim and forage in the sea.  A few days ago, Little 26 fell into a gulch and was washed away by swells. Whether she’ll swim to safety somewhere and learn to eat fish quickly enough to survive (which is highly unlikely), we’ll never know. But it is so unusual and amazing that an abandoned pup could find a cow that would let it steal milk, and then survive for so long afterwards.

Luckier pups with more experienced mothers will nurse continuously until they grow from their birth weight of 60-80 lbs to a weaning weight of 200-300 lbs. Protected by their knowledgeable mother, they will spend all of their time eating and sleeping, comforted with their warm mothers by their side. They’ll sleep for hours at a time, undergoing sleep apnea during which they won’t breathe for many minutes in order to save energy and prevent precious water evaporation by breathing. They’ll build up the vital blubber layer that will give them valuable nutrition in the several months they will have to fast before their first trip to sea. 
Pup with protective mother

Their idyllic life will end abruptly when their mother is impregnanted by the alpha male of the colony and departs for her own long journey in the sea to replenish her lost resources. Without the food and protection of its mother, the new weaner will have to face a harsh and difficult world. First of all, the huge amount of accumulated blubber makes it difficult for it to move around on land. It makes it a challenge getting out of the way of fighting males, and often times new weaners are brutally attacked by adult males due to displaced aggression or simply for getting in the way.
Weaner with gashes from an adult male attack (foreground)

We witnessed one such incident in Mirounga Beach when MC Hammer put a few very deep gashes in the neck of Grasshopper’s male weaner as soon as his mother left the beach. While scrambling to leave the dangerous Mirounga Beach territory, Grasshoper’s weaner fell several feet into Log Channel, a narrow gulch in which animals can often become trapped until higher tides and swells can help wash them back up onto safer land. The injured weaner spent several days bleeding and shivering in Log Channel, occasionally getting carried out toward the perilous sea by the strong waves. Surprisingly, he managed to ride one of the waves back out of Log Channel onto the safety of the Isthmus one morning. Although he was safer on land, now he had to face the aggressive gulls who incessantly pecked at the infected flesh of his neck wounds. 
Grasshopper's weaner with neck injuries

Sometimes the gulls can wear down an injured pup in this way, and we have often seen gull attacks precede a pup’s untimely death. Surprisingly, Grasshopper’s weaner managed to hold on. He recovered with time and his wounds are now healed to the point of being nothing but battle scars. For now, he looks healthy and active, and spends most of his time playing with other weaners. He has even returned to Mirounga Beach and began to venture into the shallow waters by his birthplace.
Healed Grasshopper (front row, third from left) with friends

Some weaners get really, really lucky. Unwilling to accept their fate as an independent young seal with no constant source of milk, they persistently seek another source of nourishment. Sometimes, such pushy youngsters will have the good luck to find a cow that had recently lost her own pup and is willing to adopt another. Such weaners revert back to puphood and can sometimes nurse for up to 4 more weeks from their surrogate mother, growing up to twice as large as their normal cohorts – up to 600 pounds!  However, being a superweaner is not necessarily an advantage. Their large size impedes their movement on the beach, making it difficult to evade aggressive males and necessitating a longer fasting period on land before they are svelte enough to enter the sea. Last year, we witnessed MC Hammer gravely injure that season’s sole superweaner, causing her to die from horrific head wounds. This year’s superweaner had a much happier fate. He was one of our first weaned pups, born to an older cow named Kyra. He found a second mother in Ivy, a cow that was separated from her own pup early in its life. Although Ivy often seemed irritated with Superweaner’s persistent urgings for more milk, he eventually won her over and she ended up letting him nurse for 13 days! 
Superweaner with Ivy

Although he was bigger than most of the other weanlings, he did not grow to the gargantuan proportions that we saw in last year’s superweaner, which is probably a good thing since he’s been able to move around well enough to avoid danger. Right now, we can hardly tell him apart from the other weaners. Perhaps this little extra nutritional boost was all he needed for a good start in life.
Superweaner (left) with normal weaner

So what is life like for all of the other weaners? Well, it involves plenty of sleeping during the first few weeks in order to save energy and ration those precious fat reserves. They huddle in little groups called ‘weaner pods’ for protection while the adult seals are still around in the colony. 
Sleepy weaners

Once they start losing weight, the weaners become more active and start exploring their surroundings, learning how to swim, interact with each other, and all of those other vital skills that they need to survive in the sea. They learn these skills by playing in puddles, submerging their noses in muddy water and blowing bubbles, rooting around for rocks and washed-up jellyfish, picking them up and trying to chew on them. 

They learn that rocks and sand and plants are not edible, and they learn how not to swallow water or get it up their nose.  

Chewing rocks
Blowing bubbles

They learn to fight by playing with each other in little groups, lightly biting their friends’ necks, hind ends, flippers, or any other body parts that look fun to chew. 

They vocalize at each other and learn aggressive social cues from weaners that don’t seem to want company. They discover what lies behind them by tilting their heads back and rearing up as high as they possibly can by using their impressive abdominal muscles. They find out that they have hindflippers by leaning back and biting on them. These seemingly ridiculous activities build necessary skills that help them fully assess their surroundings and understanding sensations in their hind body that might mean danger from attacking predators.

After all of this time building up their strength on land, the weaners are finally drawn to the sea. Northern elephant seals are truly pelagic marine mammals, meaning that they spend the majority of their life in the ocean, traveling further, wider, and deeper than most seals, eating and even sleeping in the water. But the weaners need some training before they can go on their first long trip to sea. They start by venturing into the shallows near their natal beaches. They begin swimming clumsily in protected waters, playing together in the waves, diving down for jellyfish and other objects to play with, and chasing each other under the water.

Eventually, they’ll swim farther out, building up the strength and coordination necessary to navigate rough seas. They’ll chase fish until they learn to catch them in their mouths, although it might take them some time to learn to swallow them whole. They’ll learn to look for gentle sloping beaches where they can haul out to rest, and how to swim with speed and agility to avoid sharks. It’s hard to believe that they’ll be able to accomplish all this when we look at them now, clumsily splashing in the waters.

However, two cases that we’ve seen this year have proven to us that elephant seals can manage to survive even before they’ve completed ‘weaner training.’ One afternoon while looking for marine invertebrates, we found an unknown male pup in the intertidal area below Sand Flat. He seemed rather small, possibly having been separated from his mother by high swells before he was ready to be weaned. We put a tag in his hindflipper and dubbed him “Mystery Weaner,” although we conjectured that he could have come from the small harem across the channel on West End Island. 
Mystery weaner when we first found him

After spending several days shivering in tidepools and being bashed by high swells, he disappeared and we considered him gone. Much to our surprise, Mystery Weaner reappeared several days later on Sand Flat and has now fully integrated into the local weaner society. How he managed to survive such rough conditions, swim through the rough seas between Southeast Farallon Island and West End, and then haul out onto Sand Flat - we have no idea. But we do know that he’s doing quite well so far, although he is a little bit smaller than some of his local weaner friends. 
Mystery weaner (front row, darker animal on the right) playing with a Sand Flat weaner
One of our Sand Flat pups has had quite an exciting life as a weaner. Refusing to spend his days wallowing in the stinky puddles on Sand Flat with other clueless weaners, he opted instead to climb up to the grassy terrace above Sand Flat and explore quite different surroundings. 

He wobbled around in the grass for several weeks, at one point making it up almost to the houses.   He got some quality, undisturbed sleep in the soft grass, but eventually tired of life alone in the highlands. 

After returning to Sand Flat, he disappeared the next day in search of more adventure. Although we started thinking that he didn’t make it in the sea, he reappeared in one of the gulches on the other side of the island 10 days after we last saw him. 
'Miracle weaner' returns to the gulch

He proved to us that weaners can indeed swim and survive in the sea fairly soon after being left by their mothers, although he might be a little more precocious than the rest. And while Northern elephant seal weaners spend up to two and a half months on land (on average) before their first big trip to sea, there definitely is individual variation in their behavior.

The mortality rate for weaners in their first year of life is greater than 50%, but those that make it past that point will have a much better chance at survival since that percentage will decrease with age and skill. Many will return to this same island and the same beaches to give birth to their own pups, as we’ve seen with successful breeders such as MC Hammer and Kyra, who were both born and tagged on the Farallons. A difficult life awaits our Farallon weaners, but perhaps we’ll be lucky enough to see some of these amazing animals return here in the winters ahead.

Tuesday, March 13, 2012

Clash of the Titans

The last of the elephant seal cows departed a week ago, leaving Sand Flat entirely to the weaned pups and some straggler males that are resting up before heading out to sea. The elephant seal breeding season is technically over. Before we get into telling you all about the lives of the weaners, we thought we’d share a pretty incredible event that we witnessed during the height of the breeding season. 
Restless males on Marine Terrace at the end of the season

It was the morning of Superbowl Sunday, and we had all headed out to Sand Flat to check on the seals before spending the afternoon cooking a game-day feast and watching some football. We counted 42 cows and 34 pups on Sand Flat and 6 cows and 4 pups in Mirounga Beach. The pups were getting quite fat and a few of them were close to weaning. Just before the cows leave their weaned pups, they become receptive for mating and the alpha male of their harem will impregnate each one. Elephant seals and many other marine mammals have a fascinating reproductive strategy called delayed implantation, meaning that after the egg is fertilized, it does not implant in the uterus right away (as in most land mammals). Instead, the egg divides a few times and then pauses development for 3 or 4 months while the female regains her body weight after the breeding season fast. Delayed implantation may help synchronize all of the females' breeding cycles so that they haul out around the same time to give birth, regardless of when their egg was fertilized. Once the cows are receptive for mating, the males get quite antsy. Although the alpha male will fight to the death to protect his harem, sometimes subordinate males might sneak into the periphery of the colony and manage to mate with one of the alpha's cows. Younger males with lower dominance rank are easily chased off by the alpha bulls, often with a mere vocalization or head raise. However, sometimes the alpha will be challenged by another large male.

An alpha male with his cows


We witnessed one such spectacular challenge on Superbowl Sunday and we can tell you that it was much more impressive than the football game we saw on TV that afternoon. We could feel tension in the air that morning as the big males were all on edge. As usual, Rusty was manning Sand Flat, while the lesser-ranked Herzog was hanging out on the outskirts of the colony which we call Omega Terrace. All season we had watched Herzog defend portions of Sand Flat and Omega Terrace without Rusty chasing him off more than a handful of times, and we’d been wondering if he would rise up in the ranks to take alpha status this season or the next. Perhaps Rusty had been tolerating Herzog because he helped protect the harem from intruders, giving Rusty some much-needed breaks. After all, this was Rusty’s fourth year as the alpha male of Southeast Farallon Island, and all of the energy expenditure associated with this position was probably wearing him down. At the same time MC Hammer, the alpha bull of the small harem in Mirounga Beach, had been getting quite bored with his last few cows. The number of cows who haul out and pup in Mirounga Beach has been decreasing over the years due to the cramped conditions in this narrow beach, high swells which often washed out the pups, and MC Hammer’s notoriously aggressive nature (he’s killed quite a few pups and weaners during his alpha stint in Mirounga Beach). He’s been trying to sneak up to Sand Flat occasionally to have a go at Rusty’s and Herzog’s cows.

MC Hammer in Mirounga Beach
This particular energy-charged morning, we watched MC Hammer come up through a narrow channel called the Isthmus towards Sand Flat that connects the two major harems. He wasn’t able to get very far since Herzog was laying just at the edge between Isthmus and Sand Flat, keeping a watchful eye for intruder males. MC Hammer paused and vocalized at Herzog. We knew that something big was brewing when Herzog did not back down.

MC Hammer (left) challenges Herzog (right)


For a moment, we watched these two gargantuan, primordial-looking creatures rear up as high as they could go and look each other in the eye in total, eerie silence. We got ready for one of nature's most amazing spectacles.

The two males size each other up

Herzog struck the first blow and although MC Hammer did retaliate, it was clear from the start that Herzog was the more dominant male. For a while, the only sounds we heard were the thuds and slaps as the bulls struck each others' throats with their teeth. Noses were flying everywhere. MC Hammer got backed into a corner and almost fell down into a gulch called Log Channel, where he very likely would have been trapped and killed. In fact, two males were killed during battles in Log Channel in this way in 2007 and 2010. For a few minutes, we thought that a similar fate awaited MC Hammer.

Herzog (left) bites MC Hammer's (right) neck


It didn't get as far as that. Just as MC Hammer was teetering on the edge and we were completely absorbed in the moment, getting ready to watch him fall, something huge came out of the periphery. Rusty barreled down from Sand Flat and started vocalizing at both of the other males. Immediately, both Herzog and MC Hammer turned around and took off. Herzog dashed up onto the rocks above Mirounga Beach while MC Hammer ran back down to his own harem.
Rusty (right), chases off Herzog (far left) and MC Hammer (middle)

Rusty chased MC through Mirounga Beach and out to the water, where we saw some huge splashes as they continued fighting under water. Finally, MC Hammer was defeated. Rusty took a break in Mirounga Beach and then headed back to patrol Sand Flat as usual. When one of us returned to the beach during Superbowl half-time, everything seemed back to normal and all of the males were back in their usual places as if nothing had happened. But we had a feeling that Herzog proved himself, and that maybe next year he will be the alpha male at Sand Flat. MC Hammer never ventured into Rusty's territory again this season. But Rusty's time might be running out - Northern elephant seals usually do not hold alpha rank for more than 4 years, on average. We might be seeing some big changes next season.

Rusty (right) chases MC Hammer (left) to the water. Note MC Hammer's blind left eye.

Saturday, March 10, 2012

Mandermonium with the Farallon Arboreal Salamander

Salamanders are known to be exceptional indicators of ecosystem health because they breathe through their skin making them susceptible to changes in water or air quality.  A long-term project was started on SEFI in 2006 to monitor abundance and population trends of the endemic arboreal salamanders.  Over 100 cover boards were placed at survey sites that are routinely monitored.  

We can identify individual salamanders by their spots.
 During surveys, the salamanders’ body and tail lengths are measured.  They are weighed, sexed, and photographed to help in identification.  The salamanders have uniquely patterned spots, similar to the personal attributes of our own fingerprints. 

Arboreal salamander species occur across the greater California area (from Humboldt County to Baja Mexico) and some have been found on the state’s offshore islets.  The Farallon Island salamanders are considered a subspecies due to their different spot patterns. They are called “arboreal,” or living in trees, because of their adapted propensity to climb with enlarged toe tips and a prehensile tail. They tend to be nocturnal and forage for small invertebrates on the ground, under objects, or in rock crevices.  

Photo: Kerry Froud

 After a mostly dry winter, the majority of the bi-monthly surveys on SEFI have found low numbers of salamanders.  We were beginning to worry that the ‘manders’ had vacated the island; with survey numbers dwindling to a low of 8.   The arboreal salamander is known to be more tolerant of dry conditions than most other salamanders, but it was evident that they were much happier after 2 inches of rain fell at the end of January. February’s first survey equated to a surprising jump to 71 salamanders.  At times, there were so many to process that more hands were needed to catch the wiggling critters. Eleven of those caught were immatures, affectionately called mini-manders, and 10 others were adult females with eggs (one even had 6 eggs!) which indicates that Southeast Farallon Island still has a healthy population.  

A 'Mini-Mander'

 We are currently brainstorming on ideas to expand our sampling area and feeling out other potential data points to collect during these surveys. We hope to gain a better understanding of salamander distribution and if it may be related to the abundance of sub-habitat types and prey abundance. These salamanders have given us yet another unique species to study here on the Farallones and we look forward to where this project might lead in the future.