Tolotti et al.: Vertical movements of oceanic whitetip sharks (Carcharhinus longimanus ) 
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Figure 6 
Daily temperature profiles estimated by using transmitted data from pop-up satellite archival tags used to 
track 6 oceanic whitetip sharks ( Carcharhinus longimanus) in the Indian and Atlantic oceans between 2011 
and 2012: (A) IOCS1, (B) AOCS3, (C) AOCS4, (D) AOCS5, (E) AOCS6, and (F) AOCS7. The continuous and 
dotted black lines represent the daily average depth and its standard deviation, respectively, for each shark. 
The dotted blue line represents the mixed-layer depth. 
oceanic whitetip sharks in this study (type-III behav- 
ior). Contrasting diel vertical behavior types have also 
been reported for the porbeagle ( Lamna nasus) and 
plankton-feeding basking shark ( Cetorhinus maximus) 
(Sims et al., 2005; Pade et al., 2009). These behaviors 
are believed to be linked to prey availability. The stud- 
ies cited above show that shifts in diel vertical behav- 
ior occur when the sharks change their environment, 
for example, when they move from mixed coastal wa- 
ters to well-stratified offshore waters (Pade et al., 2009; 
Queiroz et al., 2012), or when they mirror prey behav- 
ior (Sims et al., 2005). 
For the oceanic whitetip sharks tagged in our work, 
it was not possible to identify clear temporal or spa- 
tial patterns in the occurrence of the different behav- 
iors. The types of behavior alternated frequently and 
no pattern was observed across the time series (Fig. 
5, Suppl. Fig. 2). Oceanic whitetip sharks are opportu- 
nistic predators (Backus et al., 1956; Compagno, 1984), 
and the variability observed in the vertical movement 
patterns of the sharks in our study could very well be 
linked to prey distribution, as has been suggested for 
other pelagic sharks. Additional research using simul- 
taneous data collection on prey distribution and tag- 
ging experiments would be required to verify this hy- 
pothesis. A comparison of the vertical behavior of other 
pelagic sharks tagged in the same areas could also pro- 
vide useful information. 
The fast Fourier transform analysis of depth data 
from the recovered tag (shark AOCS3) revealed 2 dis- 
tinct frequency peaks, at 12 and 24 h, indicating a pro- 
nounced periodicity in the vertical movements of this 
shark (Fig. 2). The peak at 24 h confirms the diel be- 
havior, and its broad base indicates a certain degree of 
variability. Peaks corresponding to a 24-h cycle have 
been observed for other pelagic shark species, and such 
peaks are typically interpreted as evidence of diel be- 
havior (Brunnschweiler and Sims, 2012; Filmalter et 
