Thursday 6 January 2011

"What do seals eat? Seals poop, Scientists scoop!" - Lindsay Wilson writes....

The harbour seal is in decline around Scotland. Trying to understand why is a group of scientists from the University of St. Andrews Sea Mammal Research Unit.

What and how much do seals eat? This is what PhD student Lindsay Wilson is trying to work out. Travelling the coast of Scotland every 3 months, including visits to Islay, Jura and Gigha, Lindsay and her small team spend most days on the water looking for seals.

Lindsay and Ross Waddams plan their scooping strategy in Orkney where they used a helicopter to access the colonies
 Two species of seal can be found around Scotland’s coastline; the harbour (or common) seal and the grey seal. Harbour seals tend to haul-out on land in sheltered areas more accessible to man and are often therefore considered the ‘common’ seal. However, the larger Atlantic grey seal which can be found in more remote or exposed locations around Scotland’s coast is actually the most abundant species.
Over the last 10 years harbour seals have declined by one-third around Scotland (current estimate 20,000 animals) while the grey seal population has expanded dramatically (current estimate 180,000 animals). Lindsay has visited the islands twice in the last 6 months as part of a yearlong study to understand what role diet may play in the expansion or decline of Scotland’s seal populations.

Working mostly from a boat the team scans the coastline looking for seals. Once located seals are counted and identified to species before the team make their way ashore to collect seal scat (faeces). Samples are scooped into plastic bags, much like you would pick up after your dog and sent back to the lab to be analysed. Using the hard parts of prey which remain in the scat, the team can identify between different fish prey such as sandeel and cod using ear bones (otoliths) and between squid and octopus using their beaks.

Scooping action near Port Ellen

Through scat analysis Lindsay hopes to document the diet of Scotland’s harbour seals and answer a number of questions. Recent population estimates for the west coast showed no decline in seal number whereas seal counts in Orkney suggest the harbour seal population has declined by up to 65%, are the seals in these different areas eating different prey? By collecting scat over a 12 month period the team hope to understand, does diet change throughout the year? And, by understanding the diet similarities or differences between harbour and grey seals, is there competition between grey seals and harbour seals for prey?

Lindsay and her team continue to travel around Scotland collecting seal scat and will be back visiting Islay and Jura again soon to try and understand what and how much seals eat. You can follow their exploits on their web diary at

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