Tuesday, September 27, 2011

A Baby Cadborosaur No More. Part 6a: Cold Water on the 'Reptilian Hypothesis'

LeBlond and Bousfield (1995) made remarkable conclusions about the affinities of 'Cadborosaurus' (page 82):
The thinness and elongation of the body, the poikilothermy (or cold-bloodedness) which it seems to imply, and the great difference in size between the young and the adult are strong points in favour of a reptilian nature. 
I will cover why the second half of the sentence is incredibly wrong in a following post. This was originally going to be a footnote, but quickly got out of hand.

The authors hypothesized that since 'Cadborosaurus' is "long and narrow in shape" it has too much surface area to maintain a high body temperature and is thus an ectotherm. I do not find this reasoning convincing. The slimmest cetacean is the Northern Right Whale Dolphin (Lissodelphis borealis) which has a fineness ratio (maximum length/maximum thickness) of up to 10.9 (Fish 1993 - citing Leatherwood and Walker 1979) and yet it occurs in the north Pacific up to the Aleutians (Baird and Stacey 1990). Leopard seals are also quite slender and occur in Antarctica. Both of these ectotherms are compared to snakes by some observers (L. borealis is sometimes even called the "snake porpoise") despite being elongated and not truly anguilliform, which makes me wonder how literally the "snake-like" description of 'Cadborosaurus' should be taken. LeBlond and Bousfield based their image of 'Cadborosaurus' on the ultra-svelte (fineness ratio of over 30) Naden Harbour carcass, which is probably the spinal column (and attached bits) from a known species.

† LeBlond and Bousfield actually state 'poikilothermic', but this is not the correct usage; 'ectothermic' refers to relying primarily on the environment for body temperature and 'poikilothermic' refers to the ability to withstand a wide range of body temperatures. The authors also erroneously used 'homeothermic' for 'endothermic'; 'endothermic' refers to relying primarily on internal sources for body temperature and 'homeothermic' refers to organisms which keep a stable body temperature, either internally or through the environment.

LeBlond and Bousfield claim that 'Cadborosaurus' normally inhabits 5-12 °C waters with inferred ventures into colder waters (from the Naden Harbour carcass being ingested by a Sperm Whale) and to warmer waters for reproduction... more on that later. Remarkably, there is an elongated marine reptile which can tolerate these temperatures. The Pelagic Sea Snake Pelamis platura barely straggles into California due to the 18 °C isotherm, but can tolerate 16-18 °C (stops eating), 7-8.5 °C (stops swimming), 6-6.5 °C (falls into torpor), and even exposure to temperatures of 5 °C for an hour (Graham et al. 1971). Graham et al. (1971) telling describe this snake as "weak swimming", which makes me wonder, isn't an ectothermic 'Cadborosaurus' with a "very high swimming speed" contradictory?

Pelamis platura, apparently the most cold-tolerant marine reptile which isn't a turtle. From Wikipedia Commons.

The Leatherback Seaturtle (Dermochelys coriacea) is presently viewed as an uncommon seasonal resident of British Columbia (McAlpine et al. 2004) and is suggested to be occupying marginal habitat as far north as Alaska (Hodge and Wing 2000). Leatherbacks are physiologically remarkable, as they are capable of diving into waters as cold as 0.4 °C (James et al. 2006) and retain heat through a thick layer of blubber (unique among reptiles) along with their large size (Wallace and Jones 2008, Davenport et al. 2009). Leatherbacks are not the only turtles known from high latitudes; Green Seaturtles (Chelonia mydas) have been reported from British Columbia (McAlpine et al. 2004) and Alaska, and there are records of Loggerhead (Caretta caretta) and Olive Ridley Seaturtles (Lepidochelys olivacea) in Alaska as well (Hodge and Wing 2000). Hodge and Wing (2000) suggest that the non-Leatherbacks in Alaska are straying out of their tolerable range, although McAlpine et al. (2007) warn that interest in Canadian seaturtles is recent and that their status off British Columbia needs assessment.

Dermochelys coriacea from Wikipedia Commons.

Since the only British Columbian marine reptiles are about as un-'Cadborosaurus'-like as is possible, I think that speaks volumes about the probability of the 'ectothermic' hypothesis.

Previous entries:
A Baby Cadborosaur No More. Part 4: What is 'Cadborosaurus'?
A Baby Cadborosaur No More. Part 5: Hagelund's Specimen And The Cadborosaurus

Tet Zoo Coverage: 
A baby sea-serpent no more: reinterpreting Hagelund’s juvenile Cadborosaurus


Baird, R. W. and Stacey, P. J. (1990). Status of the Northern Right Whale Dolphin (Lissodelphis borealis), in Canada. The Canadian Field-Naturalist 105, 243-250. Available.

Davenport, J., Fraher, J., Fitzgerald, E., McLaughlin, P., Doyle, T., Harman, L., and Cuffe, T. (2009). Fat head: an analysis of head and neck insulation in the leatherback turtle (Dermochelys coriacea). J Exp Biol 212, 2753-2759. doi: 10.1242/​jeb.026500.

Fish, F. E. (1993). Influence of Hydrodynamic Design and Propulsive Mode on Mammalian Swimming Energetics. Australian Journal of Zoology 42, 79-101. Available.

Graham, J. B., Rubinoff, I., and Hecht, M. K. (1971). Temperature Physiology of the Sea Snake Pelamis platurus: An Index of Its Colonization Potential in the Atlantic Ocean. PNAS 68(6), 1360-1363. Available.

Hodge, R. P., and B. L. Wing. (2000). Occurrences of marine turtles in Alaska waters 1960-1998. Herpetological Review 31,: 148-151. Available.

James, M. C., Davenport, J., and Hays, G. C. (2006). Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water. Journal of Experimental Marine Biology and Ecology 335, 221–226. Available.

LeBlond, P. H. & Bousfield, E. L. (1995). Cadborosaurus, Survivor from the Deep. Victoria, British Columbia: Horsdal & Schubart.

McAlpine, D. F., James, M. C., Lien, J., Orchard, S. A. Status and Conservation of Marine Turtles in Canadian Waters. Herpetological Conservation 2, 85–112. Available.

McAlpine, D. F., Orchard, S. A., Sendall, K. A., and Palm, R. (2004). Status of marine turtles in British Columbia waters: a reassessment. Canadian Field-Naturalist 118(1), 72-76. Available.

Wallace, B. P., and Jones, T. J. (2008). What makes marine turtles go: A review of metabolic rates and their consequences. Journal of Experimental Marine Biology and Ecology 356, 8–24. Available.

Woodley, M. A., Naish, D. & McCormick, C. A. (2011). A Baby Sea-Serpent No More: Reinterpreting Hagelund's Juvenile "Cadborosaur" Report. Journal of Scientific Exploration 25(3), 495-512.

Secondary Reference:

Leatherwood, S., and Walker, W. A. (1979). The northern right whale dolphin Lissodelphis borealis Pede in the eastern North Pacific. In: Behavior of Marine Animal volume 3 (Eds H. E. Winn and
B. L. Olla.) pp. 85-141. (Plenum Press: New York.)

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