Migrating eastern North Pacific gray whale call and blow rates estimated from acoustic recordings, infrared camera video, and visual sightings

Abstract

During the eastern North Pacific gray whale 2014–2015 southbound migration, acoustic call recordings, infrared blow detections, and visual sightings were combined to estimate cue rates, needed to convert detections into abundance. The gray whale acoustic call rate ranged from 2.3–24 calls/whale/day during the peak of the southbound migration with an average of 7.5 calls/whale/day over both the southbound and northbound migrations. The average daily calling rate increased between 30 December–13 February. With a call rate model, we estimated that 4,340 gray whales migrated south before visual observations began on 30 December, which is 2,829 more gray whales than used in the visual estimate, and would add approximately 10% to the abundance estimate. We suggest that visual observers increase their survey effort to all of December to document gray whale presence. The infrared camera blow rate averaged 49 blows/whale/hour over 5–8 January. Probability of detection of a whale blow by the infrared camera was the same at night as during the day. However, probability of detection decreased beyond 2.1 km offshore, whereas visual sightings revealed consistent whale densities up to 3 km offshore. We suggest that future infrared camera surveys use multiple cameras optimised for different ranges offshore.

Estimating acoustic cue rates in bowhead whales, Balaena mysticetus, during their fall migration through the Alaskan Beaufort Sea

“…For example, Marques et al (2011) obtained 1.7 calls/whale/h for North Pacific right whales (Eubalaena japonica), but, understandably, this value was based on a very small sample size. Martin et al (2013) obtained a cue rate for minke whale (Balaenoptera acutorostrata) "boing" calls of 6 calls/whale/h, based on a single individual tracked over $12 h. Finally, in a study combining visual sightings, acoustic recordings, and infrared camera video, Guazzo et al (2019) obtained average cue rates for migrating Eastern North Pacific gray whales (Eschrichtius robustus) of 7.5 calls/whale/day, which corresponds to 0.31 calls/whale/h.…”

“…Note, however, that because this cohort segregation is not clear-cut and varies between years, our sample will likely have included whales of all sizes and both sexes, including cow-calf pairs. We have also assumed that individual cue rates do not change over the course of the autumn migration (e.g., Guazzo et al, 2019) and do not vary with whale density (e.g., Noad et al, 2017). Finally, in addition to the effects of man-made sounds on calling rates, discussed in Sec.…”

The Rapid Rise of Next-Generation Natural History

“…Autonomous recording units can be programmed for scheduled recording times over long survey durations of weeks or months without the need for direct observations, while providing permanent records of sound and increasing the quantity of survey data (Tegeler et al, 2012). Passive acoustic monitoring is a versatile approach that may be used with a variety of taxa that either vocalize or make audible movements, including birds, bats, terrestrial and marine mammals, fish, amphibians, and insects (Newson et al, 2017;Guazzo et al, 2019;Duchac et al, 2020). Recent examples of passive acoustic monitoring for next-generation natural history include tracking phenological shifts of frogs (Llusia et al, 2013) in relation to climate change, estimating population sizes of FIGURE 1 | Technology-fueled innovation that is allowing for next-generation natural history.…”

Estimating the abundance of the critically endangered Baltic Proper harbour porpoise (Phocoena phocoena) population using passive acoustic monitoring

“…These challenges are further compounded when the population of interest is small and widely dispersed. As a result, many abundance studies of such species/populations rely on technological and statistical advances as well as integrated international efforts (Borowicz et al, 2019; Cubaynes et al, 2019; Guazzo et al, 2019; Hammond et al, 2013; Johnston, 2019).…”