Byrd et al. : Strand ings as indicators of marine mammal biodiversity and human interactions 
15 
F 
Harbor porpoises 
/i=249 
.. ■*■■■■ 
G 
;■> 
Beaked whales 
n= 27 
o 
J' \ 
0 
f 
- o * *• 
k 
2617 5 0 25KUomW«i 
Figure 6 ( continued ) 
Map J: baleen whales — Eg (Eubalaena glacialis ), Ba (Balaenoptera acutorostrata ), Bb (Balaenoptera borealis), Be ( Balaenoptera 
edeni), Bp ( Balaenoptera physalus ), Mn ( Megaptera nouaeangliae), and Ub (Unknown balaenopterid). The baleen whales far from 
shore were found floating and towed to shore for necropsy when possible. 
visitors and, at times, it was a challenge to maintain 
the safety of both seals and humans. The NC stranding 
network has increased outreach efforts to educate the 
public on the needs and dangers of hauled-out seals 
and on the legal mandates to protect seals from ha- 
rassment (MMPA, 16 USC 1361). 
Anecdotal evidence suggests that there has been an 
increase in the number of seals overall on NC and VA 
beaches (S. Barco, personal observ.). No trend was de- 
tected through the years of data included in this study, 
although there was interannual variability with nota- 
bly high strandings in 2003 and 2005. Although the 
populations of some species are increasing (Waring et 
al., 2013), the drivers affecting an associated expansion 
of movements may not result in regular and increased 
movements to NC. Strandings, however, do not reflect 
the number of seals on the beach because they do not 
include healthy seals unless they were harassed. In 
addition, a standardized mechanism for reporting and 
tracking sightings, which is needed to test any hypoth- 
esized increase, has been lacking. 
Harbor porpoise Interannual variability was the prev- 
alent annual pattern for harbor porpoise strandings. 
Although harbor porpoises are known to be caught 
in gill nets (Orphanides, 2009), the number of HI-FI 
strandings was not high enough to explain increased 
strandings during some years (Hohn et al., 2013). Be- 
cause harbor seals and porpoises occur in NC during 
a similar time of year and originate from northern 
waters, their marked increases during the same years 
may be a result of the same processes. 
The temporal occurrence of harbor porpoise strand- 
ings in NC is consistent with the migration of por- 
poises out of northern areas as water temperatures 
decrease (Gaskin, 1992). The wintering grounds and 
migration patterns of harbor porpoises migrating south 
to the mid-Atlantic are poorly understood, but there 
is evidence that some porpoises may occur in offshore 
waters ( see Palka et al., 1996). Although Cape Hatteras 
has been the presumed southerly limit (see Palka et al., 
1996), 13% of strandings occurred between Cape Hat- 
teras and Cape Lookout, owing either to drifting car- 
casses or to porpoises swimming south of Cape Hatteras 
at least occasionally. Interestingly, as with strandings 
of harbor seals, most harbor porpoise strandings were 
of sexually immature individuals ( see also Hohn et al., 
2013), the drivers for which may also be age-segregated 
migration and age-specific mortality patterns. 
Harbor porpoises migrating along the western North 
Atlantic coast are susceptible to entanglement in fish- 
ing gear. Indeed in NC stranded harbor porpoises were 
