Sunday, 22 October 2017

Seals and Storms

I’m Julie, a behavioural ecologist from Australia, who now lives in the UK and has spent three seasons working on Skomer, but this is the first year I have worked for The Wildlife Trust of South and West Wales as their field worker. In the summer I was involved in monitoring the breeding success of seabirds, and during Autumn I am part of the team monitoring the Grey Seal (Halichoerus grypus) population.

Julie and pup 89

Watching seals from the cliff tops can be lots of fun, but there is also a serious side to our work. Long-term monitoring projects, such as the seal project that started in 1983, provide insight into the vulnerability of marine populations to pressures created by human-induced disturbances and climate change. These projects can help us understand how to protect and preserve the marine environments and its wildlife.

Julie conducting a site visit at South Castle Beach Cave

The seal monitoring on Skomer is conducted each autumn by a small team who:

1) maintain daily records of the number of seals that are laid out on key beaches around the island, including their age and sex;

2) document seals that are entangled with human-made materials, such as plastics, ropes and fishing line;

3) record the number of pups born at these beaches and determines their survival rates; and

4) record fatalities and probable causes of death.

Bull seal entangled in a blue pallet strap

Unfortunately, recent events on the island have led to an increase in fatalities. Earlier this week, the UK experienced ex-Hurricane Ophelia, the strongest storm since 1987. The winds and waves caused by Ophelia were phenomenal with over 16m measured at St. Ann’s Head (the weather station can’t measure more than 16m so no one knows how large the biggest waves really were). And this weekend storm “Bryan” battered the island severely once again.

Wave heights from St. Ann's Head Weather Station

There was some impact on the island infrastructure, but the effects on the seal population were much worse. Approximately two-thirds of the seals pups have died or disappeared from the monitoring beaches; that is 50 of 75 pups lost since the first storm (we haven’t yet counted what is left after storm Bryan). Those that remain appear to have injuries to their heads or bodies and often look lethargic and weak. We have also noticed pups washed up on different beaches from where they were born, which happens every year but not to such an extent. If they are still small and their mothers can’t find them they will starve. The number of adult seals hauled-out on the beaches has also decreased since the storm.

Dead seal pup trapped under boulders

Dead immature seal

While sharing this information is rather saddening, there is also some positive news to report. We found two seal pups born the day after storm Ophelia with a couple more born later in the week. Importantly, the data collected this year will be compared with other years and may increase our understanding of the influence of storm events, such as Ophelia, on the breeding population of Grey Seals.

New life after the storm

If you are interested in the seal monitoring work done on Skomer, you can read more in the 2016 report, which is available here on the WTSWW homepage.

Julie Riordan
(Field Worker)

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