Study Sites

Field work was conducted on two grey seal breeding colonies in Scotland. Both the

North Rona (59◦06’N, 05◦50’W) and the Isle of May (56◦11’N, 02◦33’W) breeding

sites are colonies that have long standing research projects monitoring them. Plasma and milk samples were taken on North Rona and the Isle of May from 2009 until 2011, and behavioural observations were also taken during this time on North Rona. Both sites were utilised for manipulation experiments with free ranging manipulations done on North Rona from 2010 to 2011. Free ranging and pen trial manipulations were performed on the Isle of May from 2010 until 2012. Additional work to generate long term sample sets and to perfect methodologies used in the field was carried out at the SMRU captive facility at the University of St Andrews, Scotland from 2011 until 2012. Plsama samples from species other than grey seals were collected

opportunistically throughout the duration of the PhD when other projects were capturing and drawing blood from individuals of interest. Both Harbour seal and Weddell seal plasma were collected via such collaborations.

2.2.1. North Rona

North Rona is a remote island in the Outer Hebrides of Scotland, 44 miles north east of the Butt of Lewis in the north Atlantic. It is a small island with shorelines ranging from rocky boulder gullies to steep cliffs 108 meters high, making access to the island

Chapter 2: General Methodology

by boat difficult. The island is uninhabited and currently managed by Scottish National Heritage as a natural nature reserve due to the island’s importance as a sea bird and grey seal breeding site. Grey seals were first studied on the island in 1938 by Fraser Darling (Darling 1939), and research on the breeding colony has been carried out almost every year from the 1950s until present day (Boyd et al 1971, Anderson et al 1975, Pomeroy et al 2005 and unpublished data). Grey seals are present on the island in the summer and winter, but the breeding season occurs from mid September until mid November and this is when the largest aggregations of seals occur over the grassy plains and rocky shores of the island. The size of the colony has declined over the time period it has been studied; from 1959 to 1968 the mean number of pups born per year was 2250 (Boyd and Campbell 1971), from 2000 to 2010 this number had dropped to 854 (SMRU unpublished data 2013).

The topography of the island makes it ideal for conducting long term behavioural observation studies on the main part of the colony, situated on the south part of the Fianuis peninsula in the shadow of Toa Rona and Fank Brae (Figure 2-1.). Wooden hides are erected on the top of Fank Brae looking down over the main colony, enabling researchers to record data on multiple animals from one position. Certain females in the colony are also caught twice during their stay as part of a long term project to monitor net lifetime reproductive success and health of the animals. This allowed samples to be obtained from both mothers (milk and plasma) and pups (plasma) during early and late lactation, which could then be analysed with the behavioural observation data taken around catching events. The island has no electricity, and power to run freezers must be generated by a portable generator, making samples storage difficult. By using a large portable freezer, large ice packs and a rigorous generator schedule, samples were kept frozen without defrosting through out the six week study periods.

Figure 2-1 Map of North Rona, with the hide location (■) and study area containing

breeding grey seals shown in grey.

2.2.2. Isle of May

The Isle of May is another offshore seal colony, located in the Firth of Forth, five miles from the east coast of Scotland. This island, like North Rona, is managed by Scottish National Heritage as a natural nature reserve due to the large sea bird and seal breeding colonies there. The island has no permanent residents but researchers are present almost year round, studying either the birds from spring to late summer or seals from autumn to winter. The island is accessible to the public during the summer but closed during the seal breeding season from mid October to late December as seals occupy most of the island during this time. There were no records of grey seals

Chapter 2: General Methodology

island had become an important colony for the seals, with the number of pups born annually increasing from 615 in 1982 (Brockie 1984) to 1968 in 1998 before

stabilising over 2000 - 2010 with a mean of 1955 pups per year (SMRU unpublished data 2013). It is thought this rapid increase in the colony’s early years was due to seals breeding on the Farne Isles being discouraged from that site and moving to this one (Brockie 1984). The colony is not concentrated in one part of the island as on North Rona, making behavioural observations on the study females that are sampled difficult. Therefore this island was used to collect a large sample set of female and pup plasma to compare with findings from North Rona. As this island does have electricity, storing samples without defrosting is far easier. Therefore the Isle of May was the site of most of the manipulation experiments that required multiple blood samples from one animal. Due to its proximity to the mainland and the relative ease of accessing the island by boat, this site was also used for all pen trial experiments as the time spent on the colony by observers could be extended if needed.

2.2.3. The Sea Mammal Research Unit Captive Facility

SMRU is located at the Scottish Oceans Institute, St Andrews and has a large Home Office licensed captive facility where up to six harbour or grey seals can be kept for up to a year. These animals are wild caught, often from nearby haul out or breeding sites, and brought into the laboratory to allow detailed study of tag design, respiration physiology, cognitive skills and learning abilities and a variety of other studies that would not be possible using wild free ranging animals. Animals are housed in outdoor seawater pools at ambient temperature and are fed a variety of fish native to Scottish waters. This study utilised five such individuals held at the facility:

Z - Adult male harbour seal caught from the Eden River and kept from 10.02.11 until November 2011.

V – Two year old male harbour seal caught from the Moray Firth and kept from 01.10.10 until 29.10.11.

W – One year old female harbour seal caught from the Moray Firth and kept from 01.10.10 until 29.10.11.

Y – Weaned male grey seal pup caught at approximately one month of age from the Isle of May and kept from 06.12.11 until December 2012.

A - Weaned female grey seal pup caught at approximately one month of age from the Isle of May and kept from 06.12.11 until November 2012.

2.2.4. Opportunistic Sampling

To gain additional baseline data on the hormone of interest, any opportunity to gain data on non-breeding adults was utilised. Several projects based at or associated with SMRU were capturing animals and sampling plasma from a variety of different phocid species during the time of this project. Basal sample sets were collected from 23 harbour seals during three separate tagging events in Scotland during 2010 and 2011. The majority (16) were taken on Shetland in August 2010, five were taken in February 2011 on the Eden River haul out in Fife and the remaining two were taken in May 2011 from the Sheildaig haul out site on the west coast of Scotland. Basal

sample sets were also collected from 23 non-breeding Weddell seals during a tagging project with the British Antarctic Survey (BAS) in the Antarctic in 2011.