FIRST PHOTOGRAPHIC EVIDENCE OF A LOGGERHEAD SEA TURTLE (CARETTA CARETTA) IN BRITISH COLUMBIA.
According to Hodge and Wing (2000), McAlpine and others (2004), and Matsuda and others (2006), C. caretta has been recorded twice in the Gulf of Alaska and south off the coast of Washington State. McAlpine and others (2004) suggested the species would at some point appear in British Columbia. In the Atlantic Ocean, C. caretta is known to stray north along the east coast of Canada off the edge of the continental shelf (McAlpine and others 2007), but in this paper we present the 1st photographic record of a live specimen along the west coast of Canada in British Columbian waters.
The 1st author (LRH) observed a putative C. caretta (Fig. 1), on 22 February 2015, 45 nm west of Tofino, BC (UTM: Zone 9, 654560 E, 5392824 N, WGS84), during pelagic seabird and marine mammal research aboard the Canadian Coast Guard ship John P Tully. The turtle was initially spotted with binoculars, and was floating at the surface approximately 300 m from the ship. The specimen, estimated at 2/3 m long (from snout to tip of shell) with a significant layer of algal growth on its head and carapace, submerged after the ship approached. Sea surface temperature in the area was between 10.5[degrees] and 10.8[degrees]C (Marie Robert, Fisheries and Oceans Canada (DFO), pers. comm.).
The turtle had a large head and broad heart-shaped carapace with the widest part of the carapace skewed to the anterior 1/3 (Fig. 1). The individual's head was large (approximately 14 of overall body width) and triangular in shape; both characteristics are more consistent in Loggerhead Sea Turtles than in any other species (Pritchard and Mortimer 2000). The carapace shape compared closely to that of either C. caretta or L. olivacea. The turtle's carapace (Fig. 2A, Fig. 2B) also had a prominent peak running along the midline like that of a sub-adult C. caretta. In transverse section, the carapace of adult L. olivacea is fairly flat across the midline (Richardson 1997), as is a comparable sub-adult specimen of L. olivacea with a 70-cm carapace (Royal British Columbia Museum herpetology specimen 2065).
The color and distribution of the carapace scutes could not be determined due to the amount of algal growth (Fig. 1, Fig. 2). However, we determined that there were 4 parietal scales and an interparietal scale, which lacked algal cover and were a red-brown color with lighter cream to yellow margins (Fig. 2B). The combination of red-brown color, and the 4 parietal scales and interparietal scale is consistent with C. caretta (Matsuda and others 2006; Lee and others 2014), rather than with L. olivacea or C. mydas. The scales on the nape of L. olivacea are grey-olive, yellow-brown to olive-brown (Stebbins 1985; Matsuda and others 2006), and the margins of the large scales on the nape are far less conspicuous. Chelonia mydas tend to have 2 large sub-rectangular parietal scales and no interparietal scale.
Based on shape of the carapace, relative head size, the color and pattern of parietal scales, and the prominent interparietal scale, we concluded that this individual was the 1st confirmed C. caretta for Canadian Pacific waters.
Caretta caretta has a cosmopolitan distribution throughout temperate, subtropical, and tropical waters of the Atlantic, Pacific, and Indian Oceans. In the North Pacific, the species nests almost exclusively in Japan (Kamezaki and others 2003). Upon hatching, C. caretta carry out an extensive developmental migration, traveling from nesting areas in Japan to distant developmental and foraging habitats in the central and eastern North Pacific (Bowen and others 1995; Kobayashi and others 2008). After spending years foraging in these regions, C. caretta return to their natal nesting beaches in Japan for reproduction and remain in the western Pacific for the remainder of their life cycle (Nichols and others 2000; Kamezaki and others 2003).
Caretta caretta is listed globally as Vulnerable by the 1UCN Red List of Threatened Species, with the North Pacific population listed as of Least Concern (Casale and Tucker 2017). In Canada, C. caretta is listed as Endangered under the Federal Species at Risk Act, but no status is afforded to Pacific populations. In the United States, C. caretta in the North Pacific is considered a distinct population segment (DPS) and is listed as Endangered under the US Endangered Species Act (Federal Register 2011).
The presence of C. caretta in British Columbia increases the province's marine turtle diversity to 4 species. As suspected for C. mydas and L. olivacea, this individual may have strayed north in a plume of warm water, subsequently becoming stranded in 10[degrees]C water in which it was likely unable to thermoregulate and suffered from "cold stunning". Most sea turtles wash onshore dead or moribund in autumn to early winter. The survival of this animal into February is unusual, and its fate is unknown.
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Halpin Wildlife Research, Vancouver, BC V6G 1J3 Canada; Current address: School of Biological Sciences, Monash University, VIC 3800, Australia (LRH), Luke.Halpin@gmail.com; Southwest Fisheries Science Center, NOAA - National Marine Fisheries Service, 8901 La Jolla Shores Drive, La Jolla, CA 92037 USA (JAS); Royal British Columbia Museum, 675 Belleville Street, Victoria, BC V8W 9W2 Canada (GFH). Submitted 17 October 2017, accepted 9 November 2017. Corresponding Editor: Robert Hoffman.
LUKE R HALPIN, JEFFREY A SEMINOFF, AND GAVIN F HANKE
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|Title Annotation:||GENERAL NOTES|
|Author:||Halpin, Luke R.; Seminoff, Jeffrey A.; Hanke, Gavin F.|
|Publication:||Northwestern Naturalist: A Journal of Vertebrate Biology|
|Date:||Mar 22, 2018|
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