Behavioral Ecology of Narwhals

Narwhals, Monodon monoceros (Linnaeus, 1758), are a gregarious species commonly found in groups or “pods” of sometimes up to 20 individuals, but most often in groups of 3-8, which are often segregated by sex. During the migratory season, smaller groups combine with other groups to form large herds. Narwhals measure 3.6-6.2 m in body length (average 4.7 m in males, 4 m in females) pectoral fins measure 30-40 cm tip to tip, and width of the tail flukes is 1-1.2

 

  1. APPROACH

 

  • Pack ice field work

We will design and build acoustic recording stations which will be set up at leads in pack ice within
high-density offshore narwhal wintering grounds. These stations will record depth-specific high
frequency calls, echolocation clicks, and buzzes on the descent, bottom portion, and ascent portion of
narwhal foraging dives. We will take two approaches to collecting acoustic data from narwhals. First,
we will deploy a 15Hz-480kHz hydrophone with pre-amplifier and recording using a National
Instruments sound card with a sample rate of 500 kHz. Recent studies using wide-band acoustic
sampling in the Northeast Atlantic have documented killer whales (Orcinus orca), the largest
delphinid, produce whistles with the highest fundamental frequencies ever reported (Samarra et al. In
Press). These ultrasonic whistles may also occur in medium sized odontocetes (i.e. narwhals) but has
never been studied. The use of this first approach will ensure that the sampling scheme used to collect �
baseline data on narwhal acoustics in the pack ice is not inherently constrained by a priori sampling
decisions (where insufficient sampling frequency results in portions of whistles being missed). Second,
we will deploy a vertical array of four calibrated lower-frequency hydrophones at a series of depths
(300-900 m) that cover the range of narwhal foraging dives. This will allow us to collect depth-specific
information on the production and frequency of regular echolocation clicks and lower level clicks
(buzzes).