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On the 13th of June 1977, an unnamed cyclone (= hurricane, typhoon) passed directly over Masirah Island. Sustained winds of 166 km.hr^-1(90 knots, 103 mph) and gusts to 222 km.hr^-1(120 knots, 138 mph) and heavy rain were recorded by the airport meteorological station. Strong winds blew from the north 02:00 - 08:30 hrs when the eye passed over, and from the south 09:15 - 11:00 hrs and then subsided to 15-20 knots. High seas and high tides preceded the storm on the 12th of June and waves were washing over the nesting area by evening. Heavy rain and storm surge completely inundated the whole nesting area for at least 12 hours during the storm. Examination of the beach on the 14th of June indicated incursion of waves from 80 - 100m inland of the normal high tide mark. I excavated across the beach to 1m depth and observed that the whole beach surface to >1m had been resorted with extensive sediment movement. Marker cairns at the north end of the beach were displaced and those at the south were completely buried. The beach pro?le changed from a steep intertidal area and elevated berm to a much ?atter pro?le with extension seawards of about 50 m and extensive ?ooding and pooling of water at the back of the beach. Large quantities of previously-exposed sand were incorporated into nearshore sandbars.

The immediate effect of the storm was to inhibit (but not completely prevent) nesting. In the week before the storm an average of 55 turtles.km^-1 (range 20-94) came ashore per night and 78.8% of those nested. On the night of the 12th a single turtle came ashore and did not nest. On the 13th(after the storm) 27 turtles.km^-1 came ashore and 36% laid eggs. Mean density of turtles emerging estimated from track counts and con?rmed by tagging was not signi?cantly different in the 10 days before the storm (mean±SE 55±17 turtles.km^-1) and the 10 days after (98±64 turtles.km^-1; Wilcoxons U test P>0.05), however there was a transient drop in nesting density on 12-14th June and then a transient rise to 150-240 turtles.km^-1 on 15th June. It appeared that turtles inhibited from nesting during the rough weather delayed nesting for a few days past their expected renesting interval. A single dead turtle was found on the 14th of June with a split carapace. Immediately before the storm, we ‘rescued’ 1-2 turtles per week that were disoriented and failed to return to the sea after nesting. In the week after the storm we rescued 3-5 turtles per day and suspect that the ?atter beach pro?le caused increased disorientation. These turtles would likely have perished without our intervention but constituted a negligible mortality of the 30,000 turtles estimated to be present (Ross 1998).

All our marked nests and, as best we could establish by extensive excavation, 100% of all nests in the beach on the 13th of June were destroyed by inundation or exposure. The timing of the storm occurred about 45 days after first nesting and immediately prior to expected first hatching and many destroyed eggs contained well developed embryos. The number of eggs per nest (mean ± 2SE) was not signi?cantly different before (106.5 ± 6.9) and after (108.5 ± 12.7) the storm or different from the overall multi-year clutch size estimate for this population (107 ± 3). Site tenacity (distance between 2 consecutive nests) was calculated from nesting location of 87 tagged turtles that nested within 10 days either side of 13 June; 13 with two nests prior to the storm, 52 with a nest before and a nest after and 22 with two nests following the storm. Mean inter-nest distances were respectively (mean ± 2SE) 660m ± 250m, 890m ± 190 and 860m ± 190 and not signi?cantly different. Turtles were apparently able to locate their preferred nesting area along the beach equally well before and after the storm.

Based on estimated numbers of turtles nesting in 1977, estimated nests per female and the proportion of the nesting season occurring before and after the storm, I calculated that around 43% of the eggs laid in 1977 were lost due to the hurricane. This roughly extrapolates to 6.9 million eggs or about 276 metric tonnes of eggs destroyed in the 1977 season. Studies of hatchling emergence success completed in 1977 after the storm and in 1978 showed no obvious difference in the total survival (live hatchlings emerging) or distribution of failed eggs and nests due to different causes. Overall, ‘normal’ hatchling emergence success of C. caretta at Masirah in 1977-1978 was 24% (Ross & Barwani 1981; Fig. 5 therein). Continued study and monitoring of nesting at Masirah 1978-1986 showed population ?uctuations (Ross 1998) but no obvious signal that can be attributed to reduced hatchling production in 1977.

Within two months, wave action associated with the SW monsoon restored most of the beach to its previous steep pro?le. An exception was an area 2 km south of the beach where the displaced sediments that formed sandbanks immediately offshore impeded wave action. This section retained the ?at post-storm pro?le which resulted in reduced nesting densities (estimated by weekly track counts of 40-60 turtles.km^-1.night^-1) compared with the rest of the beach (often exceeding 100 turtles.km^-1.night^-1, Ross 1998). Turtles apparently avoided this low pro?le. Beach pro?le may be an important component of preferred nesting beaches (Stancyk & Ross 1978) that can be affected by hurricanes.

The effect of this severe hurricane on C. caretta nesting at Masirah Island in 1977 was transient disturbance of nesting and loss of eggs laid before the storm. However, adult fecundity, nesting periodicity, and nest site location were not changed and adult mortality was negligible. The majority of the nesting beach quickly returned to its normal structure and pro?le. The wide distribution of sea turtle nesting beaches throughout the tropical zone subject to severe storms suggests that these are a normal and passing disturbance to nesting sea turtles to which they are well adapted.

ROSS, J.P. 1998. Estimations of the nesting population size of loggerhead sea turtles, Caretta caretta, Masirah Island, Sultanate of Oman. In: Epperly, S.P. & J. Braun (Compilers) Proceedings of the 17th Annual Sea Turtle Symposium. U.S. Dept. Commerce. NOAA Tech memorandum NMFS-SEFSC-415. pp. 84-87.

ROSS, J.P. & M.A. BARWANI. 1982. Review of sea turtles in the Arabian area. In: Bjorndal K. (Ed.) The Biology and Conservation of Sea Turtles. Smithsonian Institution Press, Washington D.C.:373-383.

STANCYK, S. & J.P. ROSS. 1978. Analysis of sand from Green turtle nesting beaches on Ascension Island. Copeia 1978: 93-99.