Thursday, August 30, 2012

Youngsters Starting to Come Ashore

Unlike last year, as August draws to a close, almost all of the big male elephant seals have already set off in search of food.

Click here for photos of some of these big males as they went about their daily business before leaving in search of food.

And click here to see adult male elephant seals in their underwater environment.

So far only a few of the next group of 'vacationers' have ventured ashore. These first early-bird arrivals of the Fall Haul-Out are some of this year's weaners and youngsters, born 2-3 years ago.

Click here to see photos of these early arrivals.

Although some of these young elephants seals of both sexes are relaxing and sleeping, some of the more energetic puppy-like young males are already getting into dominance bouts of playful wrestling.

Click here for video of young males play-wrestling.

A few of the more adventuresome young males, on the other hand, like to test themselves by engaging slightly older male members of the group in challenges. Instead of being really aggressive, these older young males, however, tend to usually act amused and take it easy on these upstart youngsters.

Click here to see video of youngsters challenging slightly older elephant seals in a narrow inlet.

In the coming weeks, as the Fall Haul-Out gets into full swing, more and more youngsters will come ashore to relax and wrestle, and along with them, will also come some pregnant adult females and sub-adult males. ( The Fall Haul-Out usually lasts from September into November. )

Wednesday, August 15, 2012

Vibrissae AKA Whiskers

Not only are the whiskers or vibrissae on the elephant seal thought to act as natural sensors helping this marine mammmal to accurately gauge its distance from various things in its surroundings, but they also appear to enhance its amazingly sensitive ability to detect all sorts of vibrational waves created by movement both on land and in the sea.

Vibrissae, the plural form of vibrissa, comes from the Latin verb vibrare meaning to shake/vibrate.

Elephant seals have 3 sets of vibrissae/whiskers:
          1. mystacial ( on each side of the nose )
          2. rhinal ( on the upper bridge of the nose )
          3. supraorbital ( above the eyes )

These bristly yet sensitive whiskers, which are very dark/black on pups and youngsters, are thicker and longer than the other hairs on the elephant seal's body. They also seem to be the longest on the youngsters between the ages of 2 and 4 years old. Instead of being smooth like the body hairs, they are beaded with wavy bumps of repeating sequences of crests and troughs along their lengths and are supplied with blood and nerves via the muscles attaching them to the elephant seal's head. It appears as though the elephant seals can manipulate each whisker individually or as a group.

Scientists speculate that the wavy beaded profile of the vibrissae may be an adaptation that helps eseals when foraging in low visibility by allowing them to follow the change in water flow from the different hydrodynamic trails left by anything moving through the water.

From my observations, it would certainly appear that the elephant seal measures the exact proximity of its surroundings, regardless if the object is animate or inanimate, with the aid of these natural sensors, its vibrissae.

When startled or protesting, all of the elephant seal's vibrissae fairly bristle, with all of them literally standing on end.

The younger elephant seals from pups through the first 3 years are especially quick to raise their vibrissae in protest or submission along with their high-pitched vocal protests. Or maybe they're just alerting others to their presence both through physical means as well as auditory.

The rhinal vibrissae, a single hair on each side of the upper part of the nasal bridge, remind me of antennae. They're nearly always erect both on land and when the elephant seal swims along the surface. Maybe they're primarily used to warn the elephant seal as to what's in its vicinity.

The supraorbital vibrissae, the ones above the eyes, are grouped in 3 specific rows with 8 or 9 of these hairs above each eye. The row closest to the eye has 4 hairs in it, the middle one 3, and the top one 2. This triangular grouping may have something to do with fine-tuning or streamlining the elephant seal's tactile sensitivity of its vibrissae.

The supraorbital vibrissae appear to alert the elephant seal as to what's behind it.

The vibrissae on the older elephant seals tend to be lighter in color and shorter as well as often displaying many colors.

The mystacial vibrissae are usually pressed down close to the elephant seal's head when he/she calls out or talks. This downward positioning appears to be an aggressive signal since in surprise, protest or retreat, the vibrissae bristle vertically outward. This vertical positioning of the mystacial vibrissae is also apparent when one elephant seal lunges aggressively toward another. ( Maybe because in combat, the big males sometimes try to bite off each other's mystacial vibrissae. )

So, to sum this up, when the mystacial vibrissae are down, it appears to mean that the elephant seal is signalling that it's preparing for aggressive behavior. Whereas, when these whiskers are bristling outwards, it means the elephant seal in question is signalling submissive behavior.

When swimming along the surface, all 3 kinds of vibrissae are often extended, probably because the elephant seal is on high alert in preparation for whatever it might encounter.

Similarly, when swimming just below the surface, the vibrissae are often extended.

These super-sensitive vibrissae may even aid the elephant seal in determining if the vibes given off by any creature indicate aggression, fear or simply non-interference. They may also 'tell' the elephant seal if a nearby object is inanimate.

Click here to see vibrissae being used in different situations...the last picture probably being the most amazing.