Less concentrated pressure on penguins


Extreme mobility of fur seals equal less concentrated pressure on penguins during breeding season

There was a strong El Nino this year, a climactic event that can dramatically change the weather patterns in the areas which we work.  Compared to my previous (non El-Nino) field season, the mortality rate in chicks was considerable due to strong cold winds and large amounts of snow and sub-zero temperatures, leading to many adult penguins simply abandoning their nests and heading to sea.  Unfortunately, this also included a number of our instrumented birds, resulting in the loss of the devices and the data they contained.  However, we managed to describe Chinstrap and Adelie penguin foraging behavior during the breeding season for a second season.  These data are critical in seeing how unpredictable climactic events such as El Nino impact breeding penguin foraging ecology, and in turn how these events must be considered when managing the krill fishery.  

We had expected that the fur seals would conduct at-sea feeding trips in the waters around the South Orkneys, and had hoped to be able to see the overlap between the seals and penguins, to determine whether the seasonal influx of male fur seals competed with and put stress on penguins already having to work hard to feed hungry chicks.  Some seals did, however a large proportion of the instrumented seals moved further south and west, travelling over 1,000km down the west Antarctic Peninsula as far as Adelaide Island.  This extreme mobility of fur seals means that the ecological pressure exerted on krill stocks is spread across the entire region, overlapping with commercial fishing areas and penguin breeding colonies throughout the peninsula.  The seal transmitters will continue to provide data for many months, allowing us to look in-depth at how adult male fur seals spend their time between breeding seasons.

Step by step, penguin by penguin

Photo: Frank Grebstad

Photo: Frank Grebstad

Unlike the first trip to Powell Island that revolved around instrumenting penguins, we are now tasked with working on Antarctic fur seals, the pygoscelid penguins (Adelie, Chinstrap and Gentoo’s) and southern elephant seals. Consequently, our days are naturally varied, as the work we are able to do is dictated by the weather conditions.  I shall go through in increasing order of complexity the processes by which we collect data on these animals

Southern Elephant seals:

Step #1: approach the front of a sleeping 500-1,500kg adult male elephant seal with a pair of tweezers

Step #2: secure tweezers around one whisker, and pluck.

Step #3: move backwards very quickly as the (now wide-awake) elephant seal wonders what the hell you are doing.

Simple.  But it is a test of nerve to walk up to an enormous animal with very large teeth armed with nothing but tweezers.  However, the information we get from the whisker is considerable; using chemicals that are deposited in the whisker as it grows, we are able to determine what and when (to within a few months) the animal ate.  This is crucial information, as these animals spend over 9 months a year at sea and are therefore extremely hard to observe.

Penguins (all):

Step #1: Pick up a penguin.  Preferably not an angry one, but calm ones are quite rare.

Step #2: Attach transmitters to the back of the penguin (GPS and dive recorders, both combined are about the size of a small box of matches).  This requires a small amount of superglue, some waterproof tape and is generally completed in under a few minutes.

Step #3: Release for 5-10 days

Step #4: Recapture the penguin (by spending many hours stood freezing next to a penguin colony until it decides to come back home, then run around like an idiot trying to catch something that can outsprint you and is only 40cm tall).

Step #5: Remove the devices

Step #6: Repeat at least 40-50 times on individuals from each species throughout the two month period, so you cover the three stages of breeding (egg incubation, chick care and chick fledging)

When the penguin is recaptured we also take a small blood sample, to help us describe what the individual ate during its foraging trip using the same chemical markers as found in the elephant seal whiskers.  The information from the blood combined with the location data forms a very powerful dataset telling us where and on what the penguin ate at very fine scales.

Post-breeding male Antarctic fur seals

Instrumenting these animals is the most complicated procedure we do, and consequently required the best weather conditions – why will become very apparent.

Step #1: select a suitably-sized (sleeping) adult male fur seal, weighing between 100-200kg.  At a distance of 20-30m, use a dart gun to remotely-inject the animal with a sedative.  Allow 5-10minutes for the drug to take effect before approaching the animal.

Step #2: approach with a portable gas anesthesia machine, a capture net and a very large stick.  Hopefully, if you have given the correct (weight-determined) dosage the animal will be sufficiently sedated that you can simply place the anesthetic mask on and maintain the level of anesthesia.  If you haven’t, then you have a bit of a struggle with a very unhappy seal, a net, and three grown men trying to physically restrain the animal and complete the sedation.  In very cold weather, the gaseous anesthetic would not vaporize efficiently, so we were unable to work.

Step #3: once the animal is sufficiently immobilized, including a comprehensive set of health checks (to ensure the plane of anesthesia is not too deep, that the animal is not suffering respiratory distress), we can move onto instrumentation.  A two-part epoxy glue is mixed and a “footprint” of glue the size of the base of the transmitter is applied to the back of the seal, between the two foreflippers.  The instrument is then glued in place on the back, and the glue allowed to set (which can take up to 45 minutes if the air temperature is cold enough).  While the glue is setting, a whisker is clipped from the face of the animal and a blood sample taken from its hind flipper.

Step #4: after the procedure is complete, the anesthesia is stopped and the animal allowed to recover.  We watch the animal until it has completely recovered, as other males nearby tend to like picking fights and we must protect the instrumented individual until it is capable of defending itself.  One procedure can take up to two hours to complete, and you can’t relax for a second.  We had 30 animals to instrument, so this was by far the most intense of our activities.

Being a field ecologist requires you to be able to adapt and modify equipment and procedures based on the conditions you experience, and to have the common sense and experience to know when not to push it. In spite of how simple my outlines appear, it’s an intensely complicated set of procedures we have to perform – all the time remembering these are wild animals and that we need to keep disturbance levels to a minimum.  The weather doesn’t make things any easier, with at best not working optimally and at worst simply not bothering to work at all. No two sets of circumstances are the same, and to paraphrase, “the only easy day was yesterday”