Table 4. A summary of pinniped mass estimation studies.

Category		Reference	Species	Key Measurements	N	Mass-Estimation Error A
Morphometric		Hofman 1975	LS,WS,RS,CES	Length, Girth2	31	± 8.1%
		Kooyman and Castellini 1990	WS	Length, Girth2	12	Not Reported B
		Castellini and Calkins 1993	SSL	Length, Girth2	390	± 0.98%
		Van den Hoff et al. 2005	LS	Length, Girth2	51	± ~34% C
Photogrammetric	Single Camera	Hayley et al. 1991	NES	Side Area, Girth Area, Length	70	± 12%
		Bell et al. 1997	SES	Girth Area, Side Area	45	± 4.71% D
		McFadden et al. 2006	MS	Girth Perimeter, Lateral Perimeter	26	Not Reported E
		Ireland et al. 2006	WS	Overhead Width, Side Area, Side Height	73	± 13.8%
		Meise et al. 2014	GSL	Adjusted Length, Girth	♂ 15	± 7.46% F
					♀ 21	± 13.54% G
		This Study	LS	Overall Length, Umbillicus Width	15	± 4.4%
	Stereo	Waite et al. 2007	SSL	Length, Girth2	53	± 9.0%
		de Bruyn et al. 2009	SES	Volume	13–40	± 0.57–8.54%

^A “Mass Estimation Error” represents the lowest error from a given study derived either by cross validation, or residual standard error. Species: leopard seal (LS), Weddell seal (Leptonychotes weddellii, WS), Ross seal (Ommatophoca rossii, RS), crabeater seal (Lobodon carcinophaga, CES), Steller sea lion (Eumetopias jabutus, SSL), northern elephant seal (Mirounga angustirostris, NES), southern elephant seal (Mirounga leonina, SES), Hawaiian monk seal (Monachus schauinslandi, MS), Galapagos sea lion (Zalophus wollebaeki, GSL).

^B R² = 0.87.

^C based on the reported back-transformed error of 120 kg for an approximately 350 kg seal.

^D error reported as 95% confidence intervals (CI).

^E error was reported as a 95% CI of ±5 kg, but mean true mass not reported; therefore the range of potential error is extremely large.

^F based on reported errors for a 75 kg male.

^G based on reported errors for a 65 kg female.