Snover and Hohn: Validation and interpretation of skeletal marks in Caretta caretta and Lepidoche/ys kempn 



689 



Table 2 



Regressions equations and statistics from correlations between dimensions of the humerus and notch-to-tip straight carapace 

 length (SCL, cm) in loggerhead and Kemp's ridley sea turtles. All F statistics are significant at P<0.005. 



Humeral measurement 



Model equation 



SE slope 



Loggerhead sea turtles In =243) 

 Maximal length (ML, mm) 

 Longitudinal length ILL, mm) 

 Proximal width (PW. mm) 

 Deltopectoral crest width (DCW, mm) 

 Site of sectioning width ISW, mm) 

 Site of sectioning thickness ( ST, mm) 

 Distal width (DW, mm) 

 Mass(M, g) 



Kemp's ridley sea turtles (rc=262) 

 Maximal length (ML, mm) 

 Longitudinal length (LL, mm) 

 Proximal width iPW, mm) 

 Deltopectoral crest width (DCW, mm) 

 Site of sectioning width ( S W, mm ) 

 Site of sectioning thickness (ST. mm) 

 Distal width ( DW, mm) 

 Mass (M, g) 



SCL = 0.44xA/L + 5.97 

 SCL = 0.47xLL + 4.85 

 SCL = 1.06xPW + 7.31 

 SCL= 1.69xDCW + 6.04 

 SCL = 2.38xSW + 5.48 

 SCL = 4.13xST + 11.62 

 SCL = 1.28xZW+5.43 

 ln(SCL) = 0.30xln(M) + 2.94 



SCL = 0.43xML + 4.69 

 SCL = 0.47xLL + 3.11 

 SCL = 1.12xPW+4.39 

 SCL = 1.69xDCW + 3.35 

 SCL = 2.48xSW + 2.74 

 SCL = 4.16xST+ 4.79 

 SCL= 1.36xDW+ 0.227 

 LNiSCL) = 0.30xLN(M) + 2.89 



interruption of hibernation (Hemelaar and van Gelder, 

 1980). In this instance little bone deposition would 

 occur and the layers would not be distinct from each 

 other over the entire bone, thus giving the appearance 

 of a bifurcating LAG (Hemelaar and van Gelder, 1980). 

 The third interpretation of double or bifurcating LAGs 

 is that they result from extreme decreased growth over 

 the active period, which places annual LAGs very close 

 to each other and in some cases they appear to merge 

 (de Buffrenil and Castanet, 2000). 



With the first two interpretations, a double or bifur- 

 cating LAG would be counted as one for the purposes of 

 age estimation, whereas the third interpretation would 

 necessitate counting each LAG or bifurcating branch 

 separately. Coles et al. (2001) interpreted a bifurcat- 

 ing LAG as one LAG in an adult loggerhead sea turtle 

 that was recovered 8.25 years after it had been injected 

 with oxytetracycline. In cross-sections of the humerus, 

 Coles et al. (2001) reported seven LAGs following the 

 tetracycline mark, six plus the bifurcating LAG. The 

 animal was marked on 20 June 1989 and recovered 

 dead on 22 September 1997. It is reasonable to assume 

 that, as with Kemp's ridley sea turtles from the same 

 region, the LAGs form in the spring, and Coles et al. 

 (2001) showed that the oxytetracycline mark overlaid 

 one of the LAGs — likely the LAG deposited in spring 

 of 1989. Therefore, there should have been eight LAGs 

 deposited after the tetracycline mark, not seven, each 

 representing the spring of years 1990 through 1997. 

 In this case, then, the bifurcating mark in this bone 

 should be counted as two LAGs. 



Similarly, for splitting LAGs, where numerous thin- 

 ner LAGs branch out from what appears to be one thick 

 LAG, Francillon-Vieillot et al. (1990) examined different 

 bones from the same animal and determined whether 

 each thin LAG comprising splitting LAGs should be 

 counted as one LAG. In our analysis of the adult log- 

 gerhead sea turtle, CC-1, we observed several bifurcat- 

 ing and splitting LAGs. each of which eventually split 

 into two or more thinner LAGs. We counted each of the 

 thin LAGs as one. Because the LAG count was close to 

 the actual age of the animal, this interpretation ap- 

 pears to have been appropriate for compressed LAGs 

 in adult humeri. 



The question remains as to whether this is the ap- 

 propriate interpretation for double or bifurcating LAGs 

 in juveniles. Wild loggerhead growth rates have been 

 monitored in an ongoing mark-recapture study in Pam- 

 lico and Core Sounds in North Carolina (Epperly et al., 

 1995). Epperly et al. (1995) currently have 65 growth 

 rates for 49 juvenile loggerhead sea turtles between 45.1 

 and 81.0 cm SCL at initial capture that were at-large 

 for one year (±0.1 year). The mean annual growth rate 

 for all of the animals is 2.09 cm/yr. However, of the 

 65 growth records, 11 of them displayed an annual in- 

 crease of 0.3 cm or less in SCL (Braun-McNeill 1 ). Hence 

 it is not uncommon for juvenile loggerhead sea turtles to 



Braun-McNeill, J. 2004. Personal commun. Center for 

 Coastal Fisheries and Habitat Research, National Marine 

 Fisheries Service, NOAA, 101 Pivers Island Rd., Beaufort, 

 NC 28516 



