Table 7.

Diel differences in the behaviour of Cuvier's beaked whales using paired t-tests of the median values of each parameter. Deep dives are greater than 800 m, shallow dives are to depths of 50–800 m and surface intervals are between dives of 50 or more m. Paired t-tests are conducted on individual medians, but the overall median for all animals during the day and at night is displayed for each parameter to illustrate effect sizes. p-values less than 0.05 were considered significant.

	overall median
parameter	day	night	p-value (paired t-test of individual medians)
deep dives
depth	1456 m	1456 m	0.570
duration	61.0 min	56.4 min	0.003**
dive rate	0.41 h−1	0.42 h−1	0.096
shallow dives
depth	303.5 m	240.5 m	<0.001***
duration	20.1 min	16.9 min	<0.001***
dive rate	1.49 h−1	1.18 h−1	0.009**
IDDI
median duration	84.2 min	65.1 min	0.130
maximum duration	203 min	168 min	0.439
number shallow	4 dives	2 dives	<0.001***
surface
median duration (all types)	2.1 min	2.4 min	0.321
maximum duration	15.0 min	96.5 min	0.005**
terminal duration	3.4 min	4.9 min	0.039*
first duration	2.2 min	2.5 min	0.254
intermediate duration	1.9 min	2.0 min	0.340
single duration	3.7 min	30.1 min	0.035*
per cent time in dive category
time in deep dives	41.9%	43.2%	0.463
time in shallow dives	49.4%	36.1%	<0.001***
time at surface	8.7%	20.7%	<0.001***

Significance level: *p = 0.05, **p = 0.01, ***p < 0.001.