Hector's dolphins (Cephalorhynchus hectori) produce both narrowband high-frequency and broadband acoustic signals.

Odontocetes produce clicks for echolocation and communication. Most odontocetes are thought to produce either broadband (BB) or narrowband high-frequency (NBHF) clicks. Here, we show that the click repertoire of Hector's dolphin (Cephalorhynchus hectori) comprises highly stereotypical NBHF clicks and far more variable broadband clicks, with some that are intermediate between these two categories. Both NBHF and broadband clicks were made in trains, buzzes, and burst-pulses. Most clicks within click trains were typical NBHF clicks, which had a median centroid frequency of 130.3 kHz (median -10 dB bandwidth = 29.8 kHz). Some, however, while having only marginally lower centroid frequency (median = 123.8 kHz), had significant energy below 100 kHz and approximately double the bandwidth (median -10 dB bandwidth = 69.8 kHz); we refer to these as broadband. Broadband clicks in buzzes and burst-pulses had lower median centroid frequencies (120.7 and 121.8 kHz, respectively) compared to NBHF buzzes and burst-pulses (129.5 and 130.3 kHz, respectively). Source levels of NBHF clicks, estimated by using a drone to measure ranges from a single hydrophone and by computing time-of-arrival differences at a vertical hydrophone array, ranged from 116 to 171 dB re 1 µPa at 1 m, whereas source levels of broadband clicks, obtained from array data only, ranged from 138 to 184 dB re 1 µPa at 1 m. Our findings challenge the grouping of toothed whales as either NBHF or broadband species.

Heaviside's dolphins (Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range.

The costs of predation may exert significant pressure on the mode of communication used by an animal, and many species balance the benefits of communication (e.g. mate attraction) against the potential risk of predation. Four groups of toothed whales have independently evolved narrowband high-frequency (NBHF) echolocation signals. These signals help NBHF species avoid predation through acoustic crypsis by echolocating and communicating at frequencies inaudible to predators such as mammal-eating killer whales. Heaviside's dolphins (Cephalorhynchus heavisidii) are thought to exclusively produce NBHF echolocation clicks with a centroid frequency around 125 kHz and little to no energy below 100 kHz. To test this, we recorded wild Heaviside's dolphins in a sheltered bay in Namibia. We demonstrate that Heaviside's dolphins produce a second type of click with lower frequency and broader bandwidth in a frequency range that is audible to killer whales. These clicks are used in burst-pulses and occasional click series but not foraging buzzes. We evaluate three different hypotheses and conclude that the most likely benefit of these clicks is to decrease transmission directivity and increase conspecific communication range. The expected increase in active space depends on background noise but ranges from 2.5 (Wenz Sea State 6) to 5 times (Wenz Sea State 1) the active space of NBHF signals. This dual click strategy therefore allows these social dolphins to maintain acoustic crypsis during navigation and foraging, and to selectively relax their crypsis to facilitate communication with conspecifics.

A Survey of Safety Recommendations for All-Terrain Vehicle Dealers and Track Owners in Kansas.

INTRODUCTION: All-terrain vehicles (ATVs) are associated with injury, mortality, and healthcare costs. ATV related injuries are less severe when consistent safety practices are followed, however, ATV safety regulations are varied among states. This study sought to survey Kansas ATV dealers and track owners to determine safety promotion practices. METHODS: A cross-sectional telephone survey was conducted of Kansas ATV dealers and tracks. Survey questions included promotion and sale of safety equipment, provision of ATV safety information, and respondent characteristics. RESULTS: Of those contacted, 32% of dealers and 31% of tracks responded to the survey. Most ATV dealers sell safety gear (70% - 100%) and all recommend safety gear to buyers and riders. All ATV tracks reported requiring helmets (100%) but were varied regarding other forms of safety gear. The majority of ATV dealers (77%) recommended safety courses, but only 31% of dealers and 40% of tracks offered courses. Eighty percent of ATV tracks and 52% of dealers felt they had a professional responsibility to educate riders/owners on safety. CONCLUSION: Safety promotion by ATV dealers in Kansas consistently was recommended, but often limited to the sales of safety gear (helmets and gloves) or the provision of manufacturer provided safety materials. Further, ATV dealers reported rarely offering skills tests or safety courses to buyers. In Kansas, safety promotion at the point of sale or track level could be improved to increase public awareness of ATV safety practices.