Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

Abnormal Intranuclear and Cytoplasmic Formations Associated with a Chemically Induced, Transplantable Chicken Sarcoma

Thirty GRCH/15 tumors (a 1, 2, 5, 6-dibenzanthracene-induced chicken sarcoma) were examined in the light and the electron microscope. Associated with the sarcoma were two types of abnormal intranuclear lesions, one in the form of a vacuole, the other as an aggregate containing glycogen. In the electron microscope, one type of lesion observed showed an organized microfibrillar structure. Abnormal cytoplasmic formations occurred as massed clusters of thread-like or tubular material, which gave rise to small bodies with concentric shell structure; similar bodies were found associated with vacuoles.     

A surplus no more? Variation in krill availability impacts reproductive rates of Antarctic baleen whales

The krill surplus hypothesis of unlimited prey resources available for Antarctic predators due to commercial whaling in the 20th century has remained largely untested since the 1970s. Rapid warming of the Western Antarctic Peninsula (WAP) over the past 50 years has resulted in decreased seasonal ice cover and a reduction of krill. The latter is being exacerbated by a commercial krill fishery in the region. Despite this, humpback whale populations have increased but may be at a threshold for growth based on these human-induced changes. Understanding how climate-mediated variation in prey availability influences humpback whale population dynamics is critical for focused management and conservation actions. Using an 8-year dataset (2013–2020), we show that inter-annual humpback whale pregnancy rates, as determined from skin-blubber biopsy samples (n = 616), are positively correlated with krill availability and fluctuations in ice cover in the previous year. Pregnancy rates showed significant inter-annual variability, between 29% and 86%. Our results indicate that krill availability is in fact limiting and affecting reproductive rates, in contrast to the krill surplus hypothesis. This suggests that this population of humpback whales may be at a threshold for population growth due to prey limitations. As a result, continued warming and increased fishing along the WAP, which continue to reduce krill stocks, will likely impact this humpback whale population and other krill predators in the region. Humpback whales are sentinel species of ecosystem health, and changes in pregnancy rates can provide quantifiable signals of the impact of environmental change at the population level. Our findings must be considered paramount in developing new and more restrictive conservation and management plans for the Antarctic marine ecosystem and minimizing the negative impacts of human activities in the region.     

REPRODUCTIVE SEASONALITY OF WESTERN ATLANTIC BOTTLENOSE DOLPHINS OFF NORTH CAROLINA, U.S.A.

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.     

The population structure of south-central Bougainville

The technique of population structure analysis is described and then applied to blood polymorphic, anthropometric, and demographic data collected from residents of south-central Bougainville Island, Territory of New Guinea. The results from these various analyses are relatively consistent, and support the idea that this theoretical model can be applied successfully to real sets of biological data and that valid conclusions concerning the breeding structure of human populations can be reached. A comparison of breeding structures from various parts of the world reveals how sharply subdivided the breeding structure in Melanesia is, and how relatively rapidly the coefficient of kinship declines over distance in that area.     

Skin and hair pigmentation variation in Island Melanesia

Skin and hair pigmentation are two of the most easily visible examples of human phenotypic variation. Selection-based explanations for pigmentation variation in humans have focused on the relationship between melanin and ultraviolet radiation, which is largely dependent on latitude. In this study, skin and hair pigmentation were measured as the melanin (M) index, using narrow-band reflectance spectroscopy for 1,135 individuals from Island Melanesia. Overall, the results show remarkable pigmentation variation, given the small geographic region surveyed. This variation is discussed in terms of differences between males and females, among islands, and among neighborhoods within those islands. The relationship of pigmentation to age, latitude, and longitude is also examined. We found that male skin pigmentation was significantly darker than females in 5 of 6 islands examined. Hair pigmentation showed a negative, but weak, correlation with age, while skin pigmentation showed a positive, but also weak, correlation with age. Skin and hair pigmentation varied significantly between islands as well as between neighborhoods within those islands. Bougainvilleans showed significantly darker skin than individuals from any other island considered, and are darker than a previously described African-American population. These findings are discussed in relation to prevailing hypotheses about the role of natural selection in shaping pigmentation variation in the human species, as well as the role of demographic processes such as admixture and drift in Island Melanesia.