Reproductive Seasonality of Western Atlantic Bottlenose Dolphins Off North Carolina, U.S.A.

Abstract

We describe reproductive seasonality of bottlenose dolphins in North Carolina (NC), U.S.A., using strandings data from the entire coast of NC and sighting data from Beaufort, NC and by estimating dates of birth of known females. We found a strong peak of neonate strandings in the spring (April‐May), and low levels of neonate strandings in the fall and winter. The distribution of neonate strandings was significantly different from a uniform distribution (P < 0.001, K= 3.8). We found a unimodal distribution of 282 sightings of neonates with a diffuse peak in the summer. The temporal distribution of sightings of neonates departed significantly from a uniform distribution (P < 0.001, K= 5.1). Estimated birth dates of neonates from known females occurred in May (n= 6) and June (n= 4), with a single fall birth. These methods shed light on bottlenose reproductive patterns and underscore the value of using information from multiple types of data. Clarification of bottlenose dolphin reproductive patterns, such as the seasonality of birth, may enhance our understanding of the population structure of this species in the mid‐Atlantic region.

Report of the Working Group on Population Parameters and Demography of Tursiops truncatus in the Southwest Atlantic Ocean

“…The results compiled for the SWAO support previous observations of bottlenose dolphins inhabiting coastal areas in similar latitudes (e.g. Haase and Schneider, 2001;Thayer et al, 2003), where births take place mostly during warm months. Differences on the approach used to estimate date of birth could be the reason for the slightly different result obtained across studies.…”

Strandings as indicators of marine mammal biodiversity and human interactions off the coast of North Carolina

“…There is a tendency for seasonal calving (Hohn, 1980;Thayer et al, 2003) and a concomitant high mortality of neonates (Fernandez and Hohn, 1998). The resulting preponderance of neonatal strandings can mask stranding patterns of older animals when all strandings are combined.…”

“…The resulting preponderance of neonatal strandings can mask stranding patterns of older animals when all strandings are combined. Because documentation of neonatal characteristics (see Thayer et al, 2003) has not been consistent for all strandings, length was used as a proxy. In NC, Thayer et al (2003) documented the maximum length of true neonates as 125 cm (mean=108.2 cm).…”

“…Because documentation of neonatal characteristics (see Thayer et al, 2003) has not been consistent for all strandings, length was used as a proxy. In NC, Thayer et al (2003) documented the maximum length of true neonates as 125 cm (mean=108.2 cm). Thus, all strandings <125 cm were categorized as perinates, although we recognize that this category could comprise most or all of the neonates, as well as some specimens up to 3 months of age (Fernandez and Hohn, 1998).…”

“…Another mechanism for determining species presence, and potentially relative abundance, is the monitoring of stranded animals over time, especially when monitoring can be conducted in a systematic way (Evans and Hammond, 2004;Pyenson, 2011). Marine mammal strandings (hereafter 'strandings') provide researchers with rare access to protected species and serve as an invaluable source of information on their spatiotemporal distribution (e.g., Maldini et al, 2005;Nemiroff et al, 2010), and biology (e.g., Fernandez and Hohn, 1998;Thayer et al, 2003;Gannon and Waples, 2004). In addition, stranding investigations have been critical in documenting human-induced serious injuries and mortality, such as from vessel strikes (e.g., CampbellMalone et al, 2008), fi shery entanglements (e.g., Byrd et al, 2008;Cassoff et al, 2011), and sonar effects (e.g., Jepson et al, 2005).…”