Usage of monophonic and biphonic calls by free-ranging resident killer whales (Orcinus orca) in Kamchatka, Russian Far East

Abstract

Killer whale discrete calls include types containing an overlapping high-frequency component (biphonic calls) and types without an overlapping high-frequency component (monophonic calls). In the resident killer whales of the Northeast Pacific, biphonic discrete calls exhibit higher source levels than monophonic calls, which suggests different active space and consequently different functions for monophonic and biphonic call types. In this study we investigate the potential communicative functions of monophonic and biphonic discrete calls produced by killer whales from Kamchatka (Northwest Pacific). We analyze how the usage of these calls depends on the number of pods present in the area and type of activity. Our results show that the usage of monophonic and biphonic calls in Kamchatkan killer whales depends on the number of pods in the area and is less dependent on the type of activity. Biphonic calls are more common when more than one pod is present in the area and could therefore function as markers of pod and matriline affiliation, serving mainly as cohesion signals. Monophonic calls dominated the vocalizations when a single pod was present, while in the presence of more than one pod both categories were used in equal proportions.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Biphonations are common, specifically in the form of lower-frequency burst-pulse sounds together with higherfrequency, independent FM components [203,213,214,220,223]. Populations along the Canadian British Columbia coast have been studied extensively using passive acoustics.…”

“…Their sounds have been studied in coastal British Columbia, Canada, and Washington State, USA [201][202][203][204][205][206][207][208][209][210], in California [211], in other areas of the North Pacific, including Russia [212][213][214][215][216], in the North Atlantic off Norway and Iceland [217,218], in Antarctica [219,220] and south-western Australia [16]. A geographic comparison of North Atlantic and North Pacific killer whale sound frequencies was recently published [221].…”

An analysis of pilot whale vocalization activity using hidden Markov models

“…Methods in most common use range from t-tests, ANOVA and Chi-square tests or non-parametric equivalents to regression models (Deecke et al 2005, Filatova et al 2009, Foote et al 2004, Lemon et al 2006, Luís et al 2014, Oleson et al 2007, Sjare and Smith 1986, from simple linear models to those incorporating smooth terms, random effects and generalized estimating equations (Quick and Janik 2008, DeRuiter et al 2013, Di Iorio and Clark 2010, Stimpert et al 2015, Visser et al 2016. Other authors use randomization-based methods Solow 2008, Miller et al 2009) or machine-learning classification methods such as random forest decision trees [Henderson et al 2012].…”

Responses of Kamchatkan fish‐eating killer whales to playbacks of conspecific calls

“…Both biphonic and monophonic call types were used in the vocal responses of killer whale groups on the playbacks of recordings from the same pod. In Kamchatkan killer whales, monophonic calls prevail in intrapod communication, and the rate of biphonic calls increases when more than one pod is present (Filatova et al . 2009 a ).…”

“…2007, Foote et al . 2008, Filatova et al . 2009 a ) showed that the usage of different call types depended more on the presence of other pods or matrilines rather than on the type of activity.…”