Summing the strokes: energy economy in northern elephant seals during large-scale foraging migrations

Table 1 Summary of energy costs for northern elephant seals instrumented with accelerometers (N = 22)

Migration	Seal	Average Mass (kg)	DAS (TDR)	Stroke Rate (d⁻¹)	FMR (kJ kg⁻¹d⁻¹)	Kleiber	Total E Spent (MJ)
ST: Short trip	U954	297	71.9	27840	90.7	1.28	1934
	U605	308	69.5	28548	91.1	1.30	1946
	U627	333	86.6	29972	97.4	1.42	2810
	T911	343	72.5	27423	85.8	1.26	2131
	1015	354	74.1	29100	92.9	1.37	2437
	X851	372	71.2	28674	94.6	1.42	2506
	T35	384	75.6	30385	96.6	1.46	2800
	N796A	391	72.8	28534	92.7	1.41	2640
	R541	392	77.7	29595	97.5	1.48	2973
	1733	406	78.2	27925	83.2	1.27	2642
	N796B	407	71.8	28818	92.4	1.42	2699
	W1095	433	79.5	29785	91.8	1.43	3163
	R382	466	69.3	24397	76.1	1.21	2459
LT: Long trip (pregnancy)	U458	341	222.1	22825	72.9	1.07	5519
	T730	343	218.8	23731	75.0	1.10	5623
	X106	379	230.8	21770	70.5	1.06	6170
	U754	395	221.1	23579	77.1	1.17	6727
	2036	445	224.5	19335	62.9	0.99	6287
	U203	450	224.5	18165	57.9	0.91	5841
DG: Short trip (added drag)	1234	374	100.8	34822	104.5	1.57	3932
	M780	378	78.1	34299	103.2	1.55	3044
	2370	433	76.6	35669	105.1	1.64	3484
Mean ST		376	75	28538	91.0	1.36	2549
(S.E.)		(13.5)	(1.3)	(422)	(1.7)	(0.02)	(103)
Mean LT		392	224	21568	69.4	1.05	6028
(S.E.)		(19.5)	(1.7)	(947)	(3.0)	(0.04)	(186)
Mean DG		395	85	34930	104.2	1.58	3487
(S.E.)		(19.1)	(7.8)	(399)	(0.6)	(0.03)	(256)

“Average Mass” is the seal’s mass averaged across the entire migration, based on her weight at the beginning and end of the trip. “Stroke Rate” refers to the number of flipper strokes per day averaged across the migration, and “FMR” refers to estimated field metabolic rates based on the total number of flipper strokes and a cost-per-stroke of 2.58 J kg⁻¹[23] plus HIF costs. “FMR (Kleiber)” is a multiplier of Kleiber [43] predictions of mammalian basal metabolic rate. “Total E Spent” is the total amount of energy spent during foraging. See text for equations

ISSN: 2051-3933