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.

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