An Unparalleled Sexual Dimorphism of Sperm Whale Encephalization

The sperm whale Physeter macrocephalus (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale Orcinus orca). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass

On the stranding of sperm whales at Nagapattinam,Tamil nadu coast

A whale baby female sperm whale, Physeter macrocephakis Linnaeus measuring 3.71 m and weighing about 700 kg was stranded on18th December, 1988 at Samnathanpettai near Nagapattinam . Another sperm whale was found dead and washed ashore at Vizhunthamavadi near Nagapattinam on 18th January, 1991. The stranded sperm whale was an young female of 9.70 m weighing about 5 tonnes and estimated to be around five years old

Coherence betwwen 19th century sperm whale distributions and satellite-derived pigments in the tropical Pacific

It has often been suggested that, given their large food requirements, sperm whale Physeter macrocephalus distributions should reflect the distribution of productive ocean environments, and it seems therefore that chlorophyll concentration might be a good indicator of sperm whale distribution. To examine the existence of such a relationship, and to determine over which sclaes it occurs, sperm whale density was correlated with phytoplankton pigment concentration over a range of spatial and temporal scales. Sperm whale distribution was detrmined using records of kills from 19th century Yankee whaling, and the distribution of pigment concentration from satellite colour observations averaged over 8yr interval. These measures were compared over scales of 220km square to 1780km square. The distribution of sperm whales in the temperature and tropical Pacific Ocean was associated with distributions of phytoplankton pigment over every spatial scale considered, and the coefficient of correlation increased with increasing spatial scale. However, a few exceptions to this scheme were found, implying that other factors would be of importance in some regions. This study confirmed the existence of space lag and a time lag between a peak in chlorophyll concentration and a peak in sperm whale density. It also demonstrated that over large spatial scales, and when the data are averaged over large temporal scales, chlorophyll concentration is a good indicator of sperm whale distribution and that over these scales ocean colour recorded from space could help predict areas of high or low sperm whale density

Acoustic Repertoire of Sperm Whale (Physeter macrocephalus) Bachelor Groups in the Waters Surrounding Ischia, Italy (Tyrrhenian Sea)

The subpopulation of sperm whales (Physeter macrocephalus) in the Mediterranean Sea is presently list as “Endangered”. This study is an attempt to provide detailed data on sperm whale Bachelor Groups surrounding Ischia, Italy in the Tyrrhenian Sea (Mediterranean Sea). 24 hours, 38 minutes, and 38 seconds of sperm whale Bachelor Group acoustic data was analyzed in order to describe acoustic repertoire, classify behavioral associations to acoustic types, and identify habitat-use. The data showed that the acoustic repertoire of sperm whale Bachelor Groups is dominated by Usual Clicks. Additionally, a click type that maintains an inter-click interval (ICI) in between Usual Clicks and Creaks was identified during acoustic analysis and named “Transition Clicks”. Acoustic events were categorized into Single Code and Combination Code events; representing situations where one acoustic code was heard versus situations where two or more different acoustic codes were heard simultaneously. Analysis revealed that Single Code events represented 71.25% of the sperm whale Bachelor Group acoustic repertoire. The Usual Click/ Transition Click combination represented 73.74% of Combination Code events. A significant difference was shown between time spent in Single Code versus time spent in Combination Code for Usual Clicks and for Squeals. Acoustic repertoire data revealed the possibility for a strong collaborative acoustic structure and a speculated strategy for evolutionary success among sperm whale Bachelor Groups in Ischia, Italy. Additionally, the study showed that sperm whale Bachelor Groups spend 77.87% of the analyzed time engaged in orientation/searching/foraging behavior and 1.09% engaged in socializing behaviors. Event maps revealed a ‘hotspot’ of sperm whale Bachelor Group activity in the waters to the northwest of Ischia, Italy, within the submarine Canyon of Cuma, and outside of the boundaries for the Regno di Nettuno Marine Protected Area (MPA). It is recommended that the results of this study be utilized in extending the Regno di Nettuno MPA to include the ‘hotspot’, and possible critical area, for sperm whale Bachelor Groups. The results of this study and published literature of the sperm whales in this area could be utilized to create population-specific management strategies for more effective measures in ending population decrease and preserving the species. Further research should be carried out to analyze in detail the role of Transition Clicks in sperm whale acoustics and the possibility of a collaborative acoustic structure that has yet to be displayed in any other sperm whale population worldwide

Sperm whale presence observed using passive acoustic monitoring from gliders of opportunity

Habitat use by the endangered Mediterranean sperm whale subpopulation remains poorly understood, especially in winter. The sustained presence of oceanographic autonomous underwater vehicles in the area presents an opportunity to improve observation effort, enabling collection of valuable sperm whale distribution data, which may be crucial to their conservation. Passive acoustic monitoring loggers were deployed on vertically profiling oceanographic gliders surveying the north-western Mediterranean Sea during winter 2012-2013 and June 2014. Sperm whale echolocation 'usual click' trains, characteristic of foraging activity, were detected and classified from the recordings, providing information about the presence of sperm whales along the glider tracks. Widespread presence of sperm whales in the north-western Mediterranean Sea was confirmed. Winter observations suggest different foraging strategies between the Ligurian Sea, where mobile and scattered individuals forage at all times of day, and the Gulf of Lion, where larger aggregations target intense oceanographic features in the open ocean such as fronts and mixing events, with reduced acoustic presence at dawn. This study demonstrates the ability to successfully observe sperm whale behaviour from passive acoustic monitoring gliders. We identified possible mission design changes to optimize data collected from passive acoustic monitoring glider surveys and significantly improve sperm whale population monitoring and habitat use

Measuring the Lengths of Sperm Whales of the Northern Gulf of Mexico by Wavelet Analysis of their Usual Clicks

Abstract Acoustic recordings of underwater sounds produced by marine mammals present an attractive alternative to costly and logistically complex ship based visual surveys for collecting population data for various species. The first reported use of underwater acoustic recordings in the long-term monitoring of sperm whale populations was by Ackleh et al. (Ackleh et al., 2012). The paper describes counting sperm whale clicks at different locations to track population changes over time. Analysis of sperm whale clicks offers additional insight into sperm whale populations. The echo location clicks (usual clicks) of sperm whales can be used to give an estimate of the whale’s length. The acoustic axis of the whale must be aligned with the hydrophone for accurate length estimates to be made. Most previously reported work using acoustics to measure whale lengths has been done with surface hydrophones recording clicks from a diving whale. With that geometry the whale’s acoustic axis will be approximately aligned with the hydrophone. In the case of monitoring a diving whale it is usual that most of the recorded clicks are from a single whale reducing interfering clicks from other whales. When recording clicks with bottom mounted hydrophones no whale/hydrophone orientation can be assumed. The vast majority of clicks recorded are from off axis whales and therefore produce inaccurate length measurements. It is also not unusual for several clicking whales to be recorded at the same time, producing incorrect whale length measurements due to interference between the clicks. Cepstrum Analysis is the favored technique for making acoustic whale length measurements from bottom moored hydrophones. If enough clicks are recorded from the same whale in enough different orientations, the spurious signals in off axis clicks are “averaged out”. It has been observed, however, that multiple whales clicking at the same time produced errors in the results from Cepstrum Analysis. In this paper a new method for selecting on axis sperm whale clicks from which to determine repeatable length estimates will be presented. It uses wavelet decomposition and a unique quality control test to make better whale length estimates

On a sperm whale Physeter macrocephalus washed ashore at Irumeni (Palk Bay) near Mandapam

A female sperm whale Physeter macrocephalus Linnaeus (Fig. 1) measuring 4 m, weighing 1.5 t was washed ashore in dead condition at Irumeni (Palk Bay) near Mandapam on 10-11- 2000. The length at birth of a sperm whale is about 4 meters, hence it mav be in-ferred that the present whale is a new born baby

Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles

Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing, and classified using a single low-frequency (<2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. Multiple concurrently vocalizing sperm whales, in the far-field of the horizontal receiver array, were distinguished and classified based on their horizontal spatial locations and the inter-pulse intervals of their vocalized click signals. The dive profile was estimated for a sperm whale in the shallow waters of the Gulf of Maine with 160 m water-column depth located close to the array's near-field where depth estimation was feasible by employing time difference of arrival of the direct and multiply reflected click signals received on the horizontal array. By accounting for transmission loss modeled using an ocean waveguide-acoustic propagation model, the sperm whale detection range was found to exceed 60 km in low to moderate sea state conditions after coherent array processing.National Science Foundation (U.S.)United States. Office of Naval Researc

A treasure from the past: former sperm whale distribution in Indonesian waters unveiled using distribution models and historical whaling data

This study is the first in Indonesia to assess historical sperm whale (Physeter macrocephalus ) seasonal distributions by combining historical whaling data with environmental factors associated with sperm whale habitat preferences. As current records of whale occurrence covering the whole of Indonesian waters are incomplete, we used historical whaling data summarized by Charles Haskins Townsend in 1935 to model its potential distribution for each season

Male sperm whale acoustic behavior observed from multipaths at a single hydrophone

Sperm whales generate transient sounds (clicks) when foraging. These clicks have been described as echolocation sounds, a result of having measured the source level and the directionality of these signals and having extrapolated results from biosonar tests made on some small odontocetes. The authors propose a passive acoustic technique requiring only one hydrophone to investigate the acoustic behavior of free-ranging sperm whales. They estimate whale pitch angles from the multipath distribution of click energy. They emphasize the close bond between the sperm whale’s physical and acoustic activity, leading to the hypothesis that sperm whales might, like some small odontocetes, control click level and rhythm. An echolocation model estimating the range of the sperm whale’s targets from the interclick interval is computed and tested during different stages of the whale’s dive. Such a hypothesis on the echolocation process would indicate that sperm whales echolocate their prey layer when initiating their dives and follow a methodic technique when foraging