Article

Seasonality of reproduction and length of gestation in southern right whales Eubalaena australis

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Abstract

From the seasonal occurrence of 11 stranded nconates, the earliest and latest observations of possible calving behaviour, and the seasonal incidence of calves in shore-based counts, the extent of the calving season for southern right whales off South Africa can be characterized as from late June to late October, with a peak in August. The occurrence of 89 ‘new’ calves located during monthly photogrammetric flights between July or August and November indicated that 50% were born by 1 September in 1988 and by 15 August in 1989, and that the effective calving season (in which 95.5% of calves are estimated to have been born) lasted 118 days in each year. From regression analysis of the lengths of 221 foetuses and their dates of death, and assuming a mean date of birth of 24 August, the duration of the linear phase of foetal growth is estimated to be 325 days, and the mean size at birth 6-1 m. Uncertainty over the duration of the initial, non-linear phase of foetal growth results in alternative estimates of 357 or 396 days for the total length of gestation. Foetuses of smaller females seem to be conceived later (or experience a longer initial, non-linear phase of foetal growth) than those of larger females. The apparent rarity of adult females in coastal waters in the year in which they are presumed to conceive is attributed to either a brief residence time or the possibility that conceptions may occur well outside coastal waters.

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... To determine mating strategies for right whales, population characteristics and behaviour of surface-active groups (SAGs) for North Atlantic right whales (Eubalaena glacialis) were considered. Although the behaviour that occurs among right whales in SAGs has been identified as courtship elsewhere (Ponnelly, 1967), the timing of these groups is sometimes inconsistent with Best's (1994) estimates of gestation period and observations of birth in North Atlantic right whales. Therefore, the term 'surface active group' (SAG) has been adopted here as an unbiased descriptor. ...
... Calves are born along the southeastern USA from December to February at a length of 4-5m (Kraus, 1985). The length of gestation is unknown but estimated to be between 12 and 13 months (Best, 1994). Infant right whales grow rapidly and calves reach 8-9m by the time they are weaned at the end of the first year (Hamilton et al., 1995). ...
... Questions about Surface Active Groups If conception occurs within SAGs, why are so few of the reproductively active females observed within them? Best (1994) reports that South Atlantic right whales have a gestation period of about 12-13 months. If North Atlantic right whales have a comparable gestation period, most of the SAG activity reported here is not leading to conception. ...
... Baleen whales, which comprise 16 species, are the largest animals on the planet (Lockyer, 1976), with many species undertaking annual migrations between summer feeding areas and winter breeding grounds, where foraging is largely absent (Kasuya, 1995;Lockyer, 2007). With their reproductive cycle being closely tied to their annual migratory cycle, baleen whales have evolved some of the fastest offspring growth rates among mammals (Frazer & Huggett, 1959, 1973, with both gestation and lactation being completed within approximately 1 year of conception and parturition, respectively (Best, 1994;Chittleborough, 1958;Hamilton, 1995;Huang et al., 2009;Laws, 1959;Rice, 1983). However, high offspring growth rates incur large maternal costs. ...
... We used archived data of fetal length from 207 pregnant SRW females of known length that were caught (killed) in commercial catch operations by the Soviet whaling fleet Yuri Dolgorukiy, operating in the Southern Hemisphere between 1961 and 1967 ( Fig. 1). Some of these data (155 of 207 measurements) were published in Best (1994) as References 7 (Best,Mikhalev & Brownell,in prep.) and 8 (Tormosov,pers. comm.) in Table 2 in that paper; the full data set is archived at the International Whaling Commission (Cambridge, UK). ...
... The two best-fitting GLMs for absolute and relative fetal length were then refitted by replacing day of year with days to birth. Fetal length, both absolute and relative, was then estimated as a function of days to birth, assuming a gestation period of 1 year for baleen whales (Best, 1994;Chittleborough, 1958;Laws, 1959;Rice, 1983). Model validation was done as described above (see 'Calf birth size' section) and all model assumptions were fulfilled. ...
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Key points: Baleen whales exhibit some of the fastest foetal growth rates in the animal kingdom. Despite this, the energetic cost of gestation is largely unknown, as well as the influence of maternal body size on foetal growth rates and calf birth sizes. We combined historical whaling records and drone photogrammetry data to determine foetal growth rates and birth sizes in southern right whales (Eubalaena australis), from which we estimated the cost of gestation. Calf birth size, and consequent foetal growth rates, increased positively with maternal body size. The cost of gestation was negligible for southern right whale females during the first two trimesters, but increased rapidly during the last trimester. These results show that late gestation incur a significant cost for baleen whale females, and needs to be accounted for in bioenergetic models. Abstract: The cost of reproduction greatly affects a species' life history strategy. Baleen whales exhibit some of the fastest offspring growth rates in the animal kingdom. We quantified the energetic cost of gestation for southern right whales (Eubalaena australis, SRWs) by combining whaling catch records of pregnant females with photogrammetry data on SRW mothers and calves from two breeding grounds in Argentina and Australia. The relationship between calf birth size and maternal length (ML) was determined from repeated measurements of individual females before and after giving birth. Foetal growth was determined from generalized linear models fitted to foetal length data from whaling operations between 1961 and 1967. Foetal length was converted to volume and mass, using the volume-to-length relationship of newborn SRWs calves, and published tissue composition and energy content estimates. Foetal maintenance costs (heat of gestation) and the energy content of the placenta was predicted from published relationships, and added to the foetal growth cost to calculate the total cost of gestation. Our findings showed that foetal growth rates and birth size increased linearly with ML, with calves being born at ∼35%ML. Foetal length increased curvilinearly through gestation, which resulted in an exponential increase in foetal volume and mass. Consequently, the cost of gestation was very low during the 1st (0.1% of total cost) and 2nd trimester (4.9%), but increased rapidly during the last trimester (95.0%). The heat of gestation incurred the highest cost for pregnant females (73.8%), followed by foetal growth (21.2%) and the placental energy content (5.0%). Abstract figure legend The aim of this study was to estimate the energetic cost of gestation in southern right whales. First, drone photogrammetry were used to measure the size of newborn southern right whale calves on their breeding grounds. Birth lengths were found to be ∼35% of maternal lengths. Based on this, foetal growth curves were developed from historical whaling records. The foetus grew slowly in size during the first two trimesters, but increased rapidly during the final trimester. The growth rate of the foetus was positively affected by the size (length) of the mother, with larger females having faster growing foetuses. By converting foetal length to volume and mass, and using the energetic content of different tissues (blubber, muscle, viscera and bones), the cost of foetal growth through gestation could be estimated. Placental cost and heat of gestation were calculated from the foetal size, which together equalled the cost of gestation. This article is protected by copyright. All rights reserved.
... Female 2 was first sighted in 1974 and was found dead on 20 April 1999, also with injuries consistent with ship strike; she was sighted on the calving ground with young calves in December 1990 and December 1996 (Moore et al., 2005;North Atlantic Right Whale Consortium, 2015). Dates of calf sightings (or, in the case of Female 1, size of fetus at post-mortem examination) were used to predict locations of high-progesterone areas in the baleen, based on an estimated gestation length of 12-13 months (Best, 1994) and an average baleen growth rate for adult female NARW (derived from stable isotope data; see "Stable Isotope Analysis," below). ...
... Finally, it is also possible that gestation length in NARW might be slightly longer than previously estimated. The 12-13 month gestation length widely cited for NARW is derived from estimates of the duration of the non-linear phase of fetal growth rate in the southern right whale, Eubalaena australis (Best, 1994). The NARW, a different (although closely related) species, might have a slightly different gestation length (Best, 1994;Cole et al., 2013). ...
... The 12-13 month gestation length widely cited for NARW is derived from estimates of the duration of the non-linear phase of fetal growth rate in the southern right whale, Eubalaena australis (Best, 1994). The NARW, a different (although closely related) species, might have a slightly different gestation length (Best, 1994;Cole et al., 2013). However, we emphasize that at present it is unclear whether baleen hormone profiles have precise enough time resolution for accurate measurement of gestation length. ...
Article
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Reproduction of mysticete whales is difficult to monitor, and basic parameters, such as pregnancy rate and inter-calving interval, remain unknown for many populations. We hypothesized that baleen plates (keratinous strips that grow downward from the palate of mysticete whales) might record previous pregnancies, in the form of high-progesterone regions in the sections of baleen that grew while the whale was pregnant. To test this hypothesis, longitudinal baleen progesterone profiles from two adult female North Atlantic right whales (Eubalaena glacialis) that died as a result of ship strike were compared with dates of known pregnancies inferred from calf sightings and post-mortem data. We sampled a full-length baleen plate from each female at 4 cm intervals from base (newest baleen) to tip (oldest baleen), each interval representing ∼60 days of baleen growth, with high-progesterone areas then sampled at 2 or 1 cm intervals. Pulverized baleen powder was assayed for progesterone using enzyme immunoassay. The date of growth of each sampling location on the baleen plate was estimated based on the distance from the base of the plate and baleen growth rates derived from annual cycles of stable isotope ratios. Baleen progesterone profiles from both whales showed dramatic elevations (two orders of magnitude higher than baseline) in areas corresponding to known pregnancies. Baleen hormone analysis shows great potential for estimation of recent reproductive history, inter-calving interval and general reproductive biology in this species and, possibly, in other mysticete whales.
... South African SRW skin biopsy samples (Table 1) analysed in this study are a mixture of previously collected (1990s, 2015 and 2016) and recently collected samples (2019). The recently collected samples were obtained using small stainless steel biopsy darts deployed from a crossbow (Lambertsen, 1987) on SRWs in Walker Bay, Hermanus (34°26ʹS, 19°18ʹE) and in San Sebastian Bay, Witsand (34°23ʹS 20°52ʹE; Figure S1) in September 2019 (close to the August SRW calving peak; Best, 1994). Samples were stored frozen until stable isotope analyses. ...
... SRWs feed on copepods and krill (Tormosov et al., 1998), and those that winter in South African waters are thought to have at least three summer foraging grounds (Figure 1; Best, 2007). However, these locations are based largely on illegal Soviet catch data (Tormosov et al., 1998) and Townsend's (1935) charts of open boat whaling catches, and their use by the contemporary population is not certain (Best, 2007 Given the remote location of foraging grounds of South African SRWs (see Figure 1), preventing the direct sampling of prey, we obtained δ 13 C and δ 15 N values of likely prey taxa from the SRWs' assumed historical and contemporary foraging grounds ( Figure 1; Best, 2007) from the literature (Table S1), as done in other studies using mixing models to estimate diet composition in marine mammals (i.e. ...
... SRWs feed on copepods and krill (Tormosov et al., 1998), and those that winter in South African waters are thought to have at least three summer foraging grounds (Figure 1; Best, 2007). However, these locations are based largely on illegal Soviet catch data (Tormosov et al., 1998) and Townsend's (1935) charts of open boat whaling catches, and their use by the contemporary population is not certain (Best, 2007 Given the remote location of foraging grounds of South African SRWs (see Figure 1), preventing the direct sampling of prey, we obtained δ 13 C and δ 15 N values of likely prey taxa from the SRWs' assumed historical and contemporary foraging grounds ( Figure 1; Best, 2007) from the literature (Table S1), as done in other studies using mixing models to estimate diet composition in marine mammals (i.e. Lübcker et al., 2017;Valenzuela et al., 2018). ...
Article
Rapid anthropogenic environmental change is expected to impact a host of ecological parameters in Southern Ocean ecosystems. Of critical concern are the consequences of these changes on the range of species that show fidelity to migratory destinations , as philopatry is hypothesized to help or hinder adaptation to climate change depending on the circumstances. Many baleen whales show philopatry to feeding grounds and are also capital breeders that meet migratory and reproductive costs through seasonal energy intake. Southern right whales (Eubalaena australis, SRWs) are capital breeders that have a strong relationship between reproductive output and foraging success. The population dynamics of South Africa's population of SRWs are characterized by two distinct periods: the 1990s, a period of high calving rates; and the late 2010s, a period associated with lowered calving rates. Here we use analyses of stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope values from SRW biopsy samples (n = 122) collected during these two distinct periods to investigate foraging ecology of the South African population of SRWs over a time period coincident with the demographic shift. We show that South African SRWs underwent a dramatic northward shift, and diversification, in foraging strategy from 1990s to 2010s. Bayesian mixing model results suggest that during the 1990s, South African SRWs foraged on prey isotopically similar to South Georgia/Islas Georgias del Sur krill. In contrast, in the
... months), based on observations of the reproductive tract of specimens harvested during subsistence whaling. Estimates for both species are associated with a high degree of uncertainty given the difficulty of observing small embryos within the female reproductive tract during the initial, non-linear phase of fetal growth (Best, 1994;Reese et al., 2001). Using an endocrine approach, Hunt et al. (2016a) conservatively defined gestation as "uninterrupted baleen samples with progesterone >100 ng g −1 , " and detected progesterone peaks lasting 540 and 451 days (18 and 15 months, respectively) in two North Atlantic right whales. ...
... This provisional gestation period represents 16 baleen samples, and is equivalent to approximately 384 days (12.8 months), using our timeline of baleen growth. This corresponds well to the Best (1994) estimate of a 12-13 month gestation in southern right whales-a closely related species. ...
Article
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North Atlantic right whales (Eubalaena glacialis) are highly endangered and frequently exposed to a myriad of human activities and stressors in their industrialized habitat. Entanglements in fixed fishing gear represent a particularly pervasive and often drawn-out source of anthropogenic morbidity and mortality to the species. To better understand both the physiological response to entanglement, and to determine fundamental parameters such as acquisition, duration, and severity of entanglement, we measured a suite of biogeochemical markers in the baleen of an adult female that died from a well-documented chronic entanglement in 2005 (whale Eg2301). Steroid hormones (cortisol, corticosterone, estradiol, and progesterone), thyroid hormones (triiodothyronine (T3) and thyroxine (T4)), and stable isotopes (δ13C and δ15N) were all measured in a longitudinally sampled baleen plate. This yielded an 8-year profile of foraging and migration behavior, stress response, and reproduction. Stable isotopes cycled in annual patterns that reflect the animal's north-south migration behavior and seasonally abundant zooplankton diet. A progesterone peak, lasting approximately 23 months, was associated with the single known calving event (in 2002) for this female. Estradiol, cortisol, corticosterone, T3, and T4 were also elevated, although variably so, during the progesterone peak. This whale was initially sighted with a fishing gear entanglement in September 2004, but the hormone panel suggests that the animal first interacted with the gear as early as June 2004. Elevated δ15N, T3, and T4 indicate that Eg2301 potentially experienced increased energy expenditure, significant lipid catabolism, and thermal stress approximately 3 months before the initial sighting with fishing gear. All hormones in the panel (except cortisol) were elevated above baseline by September 2004. This novel study illustrates the value of using baleen to reconstruct recent temporal profiles and as a comparative matrix in which key physiological indicators of individual whales can be used to understand the impacts of anthropogenic activity on threatened whale populations.
... As their names suggest, the three species have nonoverlapping distributions, with the NARW and NPRW restricted to their respective northern ocean basins, whereas the SRW occurs only in the southern hemisphere (Figure 12.1;Rosenbaum et al. 2000;Harcourt et al. 2019). All species of right whales differ gen et ic al ly but are morphologically similar, and share several life-history traits such as long gestation lengths (at least 12-13 months; Best 1994), long life spans (estimated at 100 years; Hamilton et al. 1998), delayed age of sexual maturity (age at first par tur ition is 8-9 years; Hamilton et al. 1998;Best et al. 2001), a typical reproductive interval of 3 years between calves ('inter-calving interval'; Burnell 2001;Kraus et al. 2001;International Whaling Commission 2012), and annual long-distance migrations from summer high-latitude feeding grounds to winter lower-latitude calving grounds (Knowlton et al. 1992;Best et al. 1993;Zerbini et al. 2016Zerbini et al. , 2018Kenney 2018;Harcourt et al. 2019). These life-history traits make the right whales especially vulnerable to extrinsic mortality and rapid environmental change (Fowler 1981;Crespo and Hall 2002). ...
... Aerial views of the entire whale can be used to quantify fat stores using 'photogrammetry' techniques to measure girth:length ratios at various defined points along the body. This technique, origin al ly developed for use from aircraft (Best 1994), is now increasingly used via cameras mounted on unmanned aerial systems (UAS) or drones (e.g. Dawson et al. 2017). ...
Chapter
Conservation physiology tools can be difficult to employ in the wild. Here we discuss developments in conservation physiology research of large whales, a taxonomic group that is famously difficult to study with traditional tools. We focus on the North Atlantic right whale ( Eubalaena glacialis ) and southern right whale ( Eubalaena australis ), two closely related species that present similar logistical challenges for research, yet differ in population status and conservation pressures. Research has advanced via a suite of creative approaches including photo-identification, visual health assessment, remote methods of assessing body condition, and endocrine research on non-plasma sample types such as faeces, respiratory vapour, and baleen. These efforts have illuminated conservation-relevant physiological questions for both species, such as discrimination of acute from chronic stress, identification of likely causes of mortality, and monitoring causes and consequences of changes in body condition and reproduction.
... Southern right whales females form breeding cohorts based on their predominant 3-year calving intervals. It is assumed that the year of calving is followed by a rest year, and then a mating year when animals usually migrate to alternative areas to their selected calving ground (Best, 1994;Burnell, 2001;Cooke, Rowntree & Payne, 2001;Brandão, Best & Butterworth, 2011;Brandão et al., 2018), although mating is also observed in Australian aggregation areas including HoB (Burnell, 2001;Charlton, 2017). ...
... Within the catalogue of known aged individuals, 23 were subsequently sighted with a calf providing information on age at first parturition. The minimum age at first parturition recorded in this study was 6 years, showing that SRWs can become sexually mature as early as 5 years old, assuming a gestation of about 1 year (Best, 1994). The homogeneity of the data was tested using double Grubs test in XLStat and the years 13 and 18 were both identified as outliers in the data with statistical significance (P = 0.0001) and were therefore excluded from the analysis. ...
Article
1. Demographic parameters were estimated for southern right whales (SRWs), Eubalaena australis, using photo-identification (photo-ID) and count data collected during annual cliff-based surveys at the Head of the Great Australian Bight (HoB), South Australia between 1991 and 2016. Photo-ID and count data were contributed from the annual aerial surveys of the south-western population in Australia (1993–2016). 2. The HoB photo-ID database included 1,186 non-calf individuals, with 459 reproductive females. HoB is an open population and represents a relative proportion (0.48–0.21) of the overall south-western population, which is decreasing with population growth. 3. No change was detected in the growth rate at HoB over time (1992–2016) and there was no significant difference when compared to the overall south-western population. The estimated mean rate of increase for all SRW was 3.2% (± 1.3) per annum and for females with a calf was 4.6% (± 1.7) per annum at HoB, compared to 5.5% (95% confidence interval (CI) 3.78, 7.36) and 6.01% (95% CI, 3.78, 7.36), respectively for the south-western population during the same period. 4. The apparent mean calving interval was 3.3 years (SD = 0.78, ± 0.14, 95% CI; 1996–2016), and a significant increase to 4 years was observed since 2015. The apparent mean age at first parturition was 9.0 years. The minimum estimated age of the oldest whale was 50 and oldest lactating female 41 years old. 5. The SRW demographic data provides information for monitoring recovery, population status, species conservation management and global comparative studies. There is a need to understand fluctuations in calving intervals, threats to the population and implications for species recovery.
... With the exception of one sighting in early December 1971, cow-calf pairs were sighted between mid-July and the end of October; one calf was born at the end of August in 1996. Despite the small number of observations, this agrees well with the calving season and the residence time of cows and young calves in other calving areas (Whitehead and Payne, 1981;Best, 1994b). Best (1994b) estimated the calving season in South Africa to range from late June to late October with most calves (95.5%) born during a period of 118 days around the mean date of birth (24 August). ...
... Despite the small number of observations, this agrees well with the calving season and the residence time of cows and young calves in other calving areas (Whitehead and Payne, 1981;Best, 1994b). Best (1994b) estimated the calving season in South Africa to range from late June to late October with most calves (95.5%) born during a period of 118 days around the mean date of birth (24 August). Cow and calf pairs are usually resident in coastal waters of South Africa for about a month before starting their southerly migration (Best and Scott, 1993), but some pairs may stay in the same bay for more than two months (Best, 1981). ...
Article
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Southern right whales were originally abundant in Namibian waters in winter and spring. They were either eradicated from the region ordriven to extremely low numbers more than a century ago. Since 1971, 36 incidental sightings and three aerial surveys confirm the regularpresence of the species within its historical calving range, between June and December. Calving has been recorded in four successive yearsand at least 10 calves were born in the area between 1996 and 1999, confirming the existence of a small established breeding population.This represents a northward extension of the hitherto known modern regular calving range in the South East Atlantic Ocean by more than1,000km.
... Right whales give birth to a single calf in the winter after a twelve-to thirteenmonth gestation period (Best 1994). The only known calving grounds are in the coastal waters of the southeastern United States between Savannah, Georgia, and St. Augustine, Florida, and most calves are born from early December through the end of March. ...
... In the North Atlantic, SAGs are seen year-round and in all known habitat areas, although they are observed much more frequently during the late summer months (Kraus and Hatch 2001). Because all calves are born during the winter, and the gestation period is estimated to be twelve months (Best 1994), then fertilization must also take place during the winter, indicating that the majority of observed SAGs in the North Atlantic are occurring out of season. Because winter is the season when the location of most right whales is unknown, the location of the mating gound(s) is also unknown. ...
... The reproductive cycle of right whales consists of gestation, a nursing phase and a resting phase, each lasting approximately 1 year (Best 1994). The typical calving interval for SRWs is therefore 3 years (Best 1994;Kenney 2009). ...
... The reproductive cycle of right whales consists of gestation, a nursing phase and a resting phase, each lasting approximately 1 year (Best 1994). The typical calving interval for SRWs is therefore 3 years (Best 1994;Kenney 2009). Because SRWs calve in coastal waters, and individual females can be reliably recognised over many years (Payne et al. 1983), the calving interval can be estimated by the observed time between successive calving events using uniquely identifiable natural markings (Burnell 2001;Cooke et al. 2003;Brandão et al. 2010a). ...
Article
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Southern right whales (Eubalaena australis) were widespread in New Zealand waters before commercial whaling in the nineteenth century caused drastic declines in their abundance and distribution. Following the cessation of whaling, the population has been recovering and is now slowly recolonising its former range. Estimates of population demographics, including reproductive output, are essential for predicting the trajectory of this population. We gathered photo-identification data on female southern right whales during annual field trips to the Auckland Islands, the principal calving area in New Zealand waters. Forty-five calving intervals were observed between 2006 and 2013 (mean interval = 3.31 years, 95% CI = 3.06–3.57). Incorporating the effects of possible missed calving events produced a plausible range of mean calving intervals from 3.17 to 3.31 years. Our results suggest that the calving interval of New Zealand southern right whales is similar to that found in populations elsewhere.
... The breeding season of southern right whales generally occurs from June to October (Best 1994 afterward (Galletti Vernazzani et al. 2017). This recent information provides increasing evidence that southern right whales are using waters off Isla de Chiloe not only during the breeding season but also likely during the feeding season for possible foraging activities. ...
... For example, in 2012, a year of warmer water temperatures not suited for abundant zooplankton, the dominant behavior was social activity. Based on an estimated gestation period of 12-13 mo Best (1994) and hypothesized that conception occurs in the winter months; therefore, the Bay may also be part of the regional mating ground proposed by Cole et al. (2013). ...
Article
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The occurrence of North Atlantic right whales (Eubalaena glacialis) in Cape Cod Bay was documented during aerial surveys between 1998 and 2013. The seasonal occurrence remained relatively unchanged during the study, spanning the January through mid‐May timeframe. The number of individual whales visiting the Bay was positively correlated with the increasing Best Cataloged Estimate (BCE), the number of photographed whales alive, with a maximum in 2011 of 56.9% (n = 277) of BCE. However, the rate of increase in number of individuals during the study was significantly greater than that of the BCE (difference in slope: 12.72; P < 0.01) suggesting that increased visitation to the Bay was due in part to a change in habitat preference. Although the demographic composition of whales observed during the study differed little from that of the cataloged whales, the proportion of calves born in the North Atlantic that were documented in the Bay increased significantly (P < 0.01). Models of random visitation demonstrated an individual preference for or rejection of the Bay by the right whales of the North Atlantic population.
... Like most baleen whales, right whales give birth to a single calf. The reproductive cycle of a southern right whale female is typically 3 yr (HoB = 3.38 yr; Burnell 2008) and consists of 1 yr of gestation (Best 1994), 1 yr of lactation (Thomas & Taber 1984, Tormosov et al. 1998) and 1 yr of recovery (replenishing energy reserves). Every year since 1991, shore-based research of southern right whales has been carried out at the HoB by the Great Australian Bight Right Whale Study (GABRWS, www. ...
Article
The cost of reproduction is a key parameter determining a species' life history strategy. Despite exhibiting some of the fastest offspring growth rates among mammals, the cost of reproduction in baleen whales is largely unknown since standard field metabolic techniques cannot be applied. We quantified the cost of reproduction for southern right whales Eubalaena australis over a 3 mo breeding season. We did this by determining the relationship between calf growth rate and maternal rate of loss in energy reserves, using repeated measurements of body volume obtained from un manned aerial vehicle photogrammetry. We recorded 1118 body volume estimates from 40 female and calf pairs over 40 to 89 d. Calves grew at a rate of 3.2 cm d⁻¹ (SD = 0.45) in body length and 0.081 m³ d⁻¹ (SD = 0.011) in body volume, while females decreased in volume at a rate of 0.126 m³ d⁻¹ (SD = 0.036). The average volume conversion efficiency from female to calf was 68% (SD = 16.91). Calf growth rate was positively related to the rate of loss in maternal body volume, suggesting that maternal volume loss is proportional to the energy investment into her calf. Maternal in vestment was determined by her body size and condition, with longer and more rotund females investing more volume into their calves compared to shorter and leaner females. Lactating females lost on average 25% of their initial body volume over the 3 mo breeding season. This study demonstrates the considerable energetic cost that females face during the lactation period, and highlights the importance of sufficientmaternal energyreserves for reproduction in this capital breeding species.
... Sexual maturaty is reached at the age of 10 years in females. Once every three years after a gestation period of 11 to 12 months a calf of up to 6m and a weight of 1500kg is born [565]. The distribution of the Southern Right Whale ranges from approximately 20°S to 55°S, but they have been observed as far south as 63°S. ...
Chapter
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... The vast majority of the whales observed in both years were mothers and calves, which is consistent with the age class composition of southern right whales in their nursing grounds in spring (September-November) (Payne, 1986;Best, 1994;Crespo et al., 2015). The proportion of adults observed in 2014 (14%) was much lower than in 2015 (38%). ...
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Whale-watching vessels can be used as platforms to collect scientific data on the natural history of cetaceans. Vessels with underwater viewing decks are exceptional and offer a unique view of the whales. We assessed the underwater viewing platform of the semi-submersible vessel Yellow Submarine that operates off Puerto Pirámides, Península Valdés, Argentina, as a platform of opportunity for southern right whale (Eubalaena australis) research. The variables considered during observations included, among others, the age class and sex of the animals observed, behavioral patterns, opportunities for individual photo-identification, distance and duration of the underwater observations and how weather conditions affected data collection. The Yellow Submarine offers a unique platform to make underwater observations of southern right whales in this calving ground, which can be particularly useful for overall visual health assessments and complementing behavioral observations made from outdoor decks of whale-watching vessels. However, the main limitations are the relatively short duration of the observations and reduced visibility in spring. Recommendations are given to counter some of these limitations and the main features and uses of this unique underwater viewing deck as a platform of opportunity for research.
... Previously published baleen progesterone profiles for both females showed good correspondence between dates of calf sightings (or, in Female 1's case, size of fetus at necropsy) and locations of extremely high progesterone content in baleen grown the year prior, based on an estimated gestation length of 12-13 mo (Best, 1994) and an estimated baleen growth rate (BGR) of 1 cm per 15 days (derived from stable-isotope data and sightings records; Hunt et al., 2016;Lysiak, 2009). Baleen progesterone remained very low during the intercalving intervals of seven years for Female 1 and six years for Female 2, likely indicating that there were not any undetected pregnancies (Hunt et al., 2016). ...
Article
Research into stress physiology of mysticete whales has been hampered by difficulty in obtaining repeated physiological samples from individuals over time. We investigated whether multi-year longitudinal records of glucocorticoids can be reconstructed from serial sampling along full-length baleen plates (representing ∼10 years of baleen growth), using baleen recovered from two female North Atlantic right whales (Eubalaena glacialis) of known reproductive history. Cortisol and corticosterone were quantified with immunoassay of subsamples taken every 4 cm (representing ∼60 d time intervals) along a full-length baleen plate from each female. In both whales, corticosterone was significantly elevated during known pregnancies (inferred from calf sightings and necropsy data) as compared to intercalving intervals; cortisol was significantly elevated during pregnancies in one female but not the other. Within intercalving intervals, corticosterone was significantly elevated during the first year (lactation year) and/or the second year (post-lactation year) as compared to later years of the intercalving interval, while cortisol showed more variable patterns. Cortisol occasionally showed brief high elevations ("spikes") not paralleled by corticosterone, suggesting that the two glucocorticoids might be differentially responsive to certain stressors. Generally, immunoreactive corticosterone was present in higher concentration in baleen than immunoreactive cortisol; corticosterone:cortisol ratio was usually >4 and was highly variable in both individuals. Further investigation of baleen cortisol and corticosterone profiles could prove fruitful for elucidating long-term, multi-year patterns in stress physiology of large whales, determined retrospectively from stranded or archived specimens.
... However, this period may lengthen to five years during poorer feeding conditions (Leaper et al. 2006). Following a gestation period of 12-13 months, calves are born between June and October, peaking in August (Best 1994). More recent work using molecular and isotopic analyses has indicated cultural (maternal) transferred fidelity to nursery grounds (Valenzuela et al. 2009), although there have been documented movements between different breeding populations (Pirzl et al. 2009). ...
... Males compete with one another for repeated mating opportunities with the focal female in an SAG, and these groups can last for several hours. Courtship activities have been reported year round; this is puzzling, because calving occurs in the winter and gestation is estimated to last 12-13 months (Best 1994). Alternative SAG functions have been proposed and are summarized in Chapter 6. ...
... Females usually calve once every 3 years (Cooke et al. 2003) and are not often seen on the calving grounds in intervening years (Payne 1986). This period includes one year in gestation (Best 1994), one year in lactation and one year recovering energy reserves to support the next pregnancy (Burnell 2001). ...
Chapter
Marine ecosystems of southern South America are very rich in species of marine mammals, with 10 pinniped and 46 cetacean species reported up to date. This chapter starts with a short description on the recorded presence and conservation status of these marine mammal species in the area. Then, in separate sections, each one corresponding to a different species, the reader will find the state of art on studies about biology, population numbers and trends, mayor threats, conservation genetics and population structure of six of the most emblematic species, extensively studied in the last decades, that inhabit southern South America coasts and waters.
... In Australia, mother-calf pairs stay on calving grounds for approximately 2 to 3 months (Burnell & Bryden, 1997). In South Africa, most calves are born in August (Best, 1994), and by November, most mother-calf pairs have already left the calving ground, suggesting that they spend from 2 to 3 months in the breeding grounds. The month of birth for calves sighted off Brazil has not been properly assessed, although the similar residence time and the fact that from October onwards mother-calf pairs predominate, suggest that the same pattern observed in South Africa also occurs in Brazil. ...
Article
Southern right whales—Eubalaena australis (Desmoulins, 1822)—migrate seasonally from high‐latitude feeding grounds to coastal breeding and calving grounds at lower latitudes such as the southern coast of Brazil. Understanding how these whales are distributed along the coast is important for monitoring their postwhaling recovery and defining management strategies. In this study, we applied Kernel density estimators to aerial survey data to determine main occurrence and concentration areas of right whales in southern Brazil and investigate inter‐ and intra‐annual distribution patterns between 2003 and 2012. Our results show considerable variation in area usage within and among years, and changes in the general distribution pattern of right whales in the last years of the study. Intra‐annually, higher concentration area tended to expand from July to September and decrease in November. Some areas stood out as high‐density areas for right whales: Ribanceira/Ibiraquera, Itapirubá Sul/Sol, and from Arroio to Gaivota. Some evidences also suggest preferential areas for mother–calf pairs. The higher concentration area of right whales in southern Brazil was estimated at 52,541 km² and the occurrence area was 682.69 km², which is the whole study area. As right whale distribution in the region is likely expanding due to this population's current recovery, our study provides essential information for management plan of the Right Whale Environmental Protection Area.
... Their diet is primarily composed of copepods (Calanus sp.) and small krill (Euphausia sp.; Tormosov et al. 1998), typically the dominant components of oceanic zooplankton, and taxa that are strongly impacted by ocean warming (Hayes et al. 2005;Nicol et al. 2008). With a gestation period of around 12 months (Best 1994), SRWs rely almost exclusively on endogenous energy stores while travelling to, residing in, and then travelling from their calving grounds. Breeding females therefore finance the late stages of gestation and early lactation almost exclusively from stored fat reserves, a period of around 7-11 weeks (Burnell and Bryden 1997;Best 2000). ...
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After near extirpation by nineteenth century whaling, New Zealand's southern right whales (Eubalaena australis) are recovering strongly, calving almost exclusively at the subantarctic Auckland Islands. Right whales are capital breeders; body condition is an important driver of their breeding success. Here we use unmanned aerial vehicles to characterise variation in individual size and shape, and to quantify the size structure of the subset of the population we sampled. Of 108 whales photographically identified we gained a comprehensive set of measurements from 63 individuals, as well as length measurements for 29 calves and six non-calf whales for which the full suite of measurements were not obtainable. Lactating females (n = 32) ranged in length from 11.84 to 15.22 m, apparent non-breeding adults (n = 9) were between 11.96 and 14.92 m, while subadults (n = 28) were between 8.82 and 11.72 m long. Calves were between 5.15 and 7.53 m. Principal component analysis of the measurement data showed that widths (particularly at the positions of 30-80% along total body length) were most influential in PC1 (40.3% variance explained). Measurements of structural features (i.e. head and flukes) related more closely to PC2 (18.2% variance explained) and PC3 (14.8% variance explained). We, therefore, interpret PC2 and PC3 as representing structural size, while PC1 represents body condition. Subadults and non-breeding adults showed more variation in body condition than lactating females, highlighting the need for this demographic to maintain their body condition within a tighter range to meet the high nutritional demands of raising calves.
... Unaccompanied adults comprised pregnant females, females in their resting year (females that are not pregnant or in nursing year), socially active groups, and solitary males or females that migrated mainly to mate. Following the peak time of birthing, mainly in August in South Africa (Best, 1994), we assumed unaccompanied whales mainly consisted of males or females that had migrated to mate or socialize. Females also can migrate the year after calving to teach their calves the migratory route to the breeding ground (Burnell, 2001). ...
Article
Santa Catarina State, in southern Brazil, is an important breeding ground for the southern right whale and it is possible to record mother‐calf pairs and unaccompanied adults that migrate to this coast to either give birth, mate, or socialize. From the geographical position of the sightings, spatial segregation was evaluated between mother‐calf pairs and unaccompanied whales. Using GAM, we analyzed 15 years of aerial survey data from 2003 to 2018. The study area (780 km2) was divided into 500 × 500 m grid cells. Whale count per grid cell was modeled using a set of explanatory variables. The explanatory variables of latitude, coast distance, seabed, and maximum SST were selected for both classes. However, coast type was also selected for unaccompanied whales, while coast linearity and bathymetric slope were additionally selected for mother‐calf pairs. The response curves fitted by models indicated a certain degree of spatial segregation, by which mother‐calf pairs remained closer to the coast, where the curve peak is reached at 500 m from the coast, compared to unaccompanied whales where the curve peaked near 1,000 m from the coast. Also, unaccompanied whales more frequently appeared in the southern boundaries of the study area, at latitudes south from 28.4°S.
... Another possibility is that the dorsal heat signature was related to the whale's pregnancy. This NARW was photo-identified as an adult female that was seen with a newborn calf 8 mo later (gestation in Eubalaena lasts approximately 12 mo; Best 1994). Pregnant NARWs are thought to have the thickest blubber layers of all age and sex classes (Miller et al. 2011) as well as increased drag due to a larger abdominal girth (McGregor 2010). ...
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The Critically Endangered status of North Atlantic right whales Eubalaena glacialis (NARWs) warrants the development of new, less invasive technology to monitor the health of individuals. Combined with advancements in remotely piloted aircraft systems (RPAS, commonly ‘drones’), infrared thermography (IRT) is being increasingly used to detect and count marine mammals and study their physiology. We conducted RPAS-based IRT over NARWs in Cape Cod Bay, MA, USA, in 2017 and 2018. Observations demonstrated 3 particularly useful applications of RPAS-based IRT to study large whales: (1) exploring patterns of cranial heat loss and providing insight into the physiological mechanisms that produce these patterns; (2) tracking subsurface individuals in real-time (depending on the thermal stratification of the water column) using cold surface water anomalies resulting from fluke upstrokes; and (3) detecting natural changes in superficial blood circulation or diagnosing pathology based on heat anomalies on post-cranial body surfaces. These qualitative applications present a new, important opportunity to study, monitor, and conserve large whales, particularly rare and at-risk species such as NARWs. Despite the challenges of using this technology in aquatic environments, the applications of RPAS-based IRT for monitoring the health and behavior of endangered marine mammals, including the collection of quantitative data on thermal physiology, will continue to diversify.
... Previous studies show increased separation of mother-calf pairs from other conspecifics on the calving grounds in both humpback whales and right whales when compared with other whales, possibly in an attempt to isolate young calves from other conspecifics [30,31]. Given the inter-birth interval of right whales (greater than 3 years) and the estimated gestation period of 11-13 months, females are unlikely to be receptive for mating while nursing a calf [32,33]. Therefore, there may be little benefit of social interactions when the calf is young. ...
Article
Mammals with dependent young often rely on cryptic behaviour to avoid detection by potential predators. In the mysticetes, large baleen whales, young calves are known to be vulnerable to direct predation from both shark and orca predators; therefore, it is possible that mother-calf pairs may show cryptic behaviours to avoid the attention of predators. Baleen whales primarily communicate through low-frequency acoustic signals, which can travel over long ranges. In this study, we explore the potential for acoustic crypsis, a form of cryptic behaviour to avoid predator detection, in North Atlantic right whale mother-calf pairs. We predicted that mother-calf pairs would either show reduced calling rates, reduced call amplitude or a combination of these behavioural modifications when compared with other demographic groups in the same habitat. Our results show that right whale mother-calf pairs have a strong shift in repertoire usage, significantly reducing the number of higher amplitude, long-distance communication signals they produced when compared with juvenile and pregnant whales in the same habitat. These observations show that right whale mother-calf pairs rely upon acoustic crypsis, potentially to minimize the risk of acoustic eavesdropping by predators.
... As the estimated gestation period for southern right whales is 10-13 months (Lockyer 1984;Best 1994), breeding is expected to occur along migratory corridors en route to wintering grounds during the austral autumn, or in the wintering grounds themselves. Due to this, it has been hypothesized that those wintering grounds from which the whales share a common feeding ground, and hence to some extent a common migratory route, could have higher levels of genetic connectivity (Carroll et al. 2015). ...
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As species recover from exploitation, continued assessments of connectivity and population structure are warranted to provide information for conservation and management. This is particularly true in species with high dispersal capacity, such as migratory whales, where patterns of connectivity could change rapidly. Here we build on a previous long-term, large-scale collaboration on southern right whales (Eubalaena australis) to combine new (nnew) and published (npub) mitochondrial (mtDNA) and microsatellite genetic data from all major wintering grounds and, uniquely, the South Georgia (Islas Georgias del Sur: SG) feeding grounds. Specifically, we include data from Argentina (npub mtDNA/microsatellite=208/46), Brazil (nnew mtDNA/microsatellite=50/50), South Africa (nnew mtDNA/microsatellite=66/77, npub mtDNA/microsatellite=350/47), Chile-Peru (nnew mtDNA/microsatellite=1/1), the Indo-Pacific (npub mtDNA/microsatellite=769/126), and SG (npub mtDNA/microsatellite=8/0, nnew mtDNA/microsatellite=3/11) to investigate the position of previously unstudied habitats in the migratory network: Brazil, SG and Chile-Peru. These new genetic data show connectivity between Brazil and Argentina, exemplified by weak genetic differentiation and the movement of one genetically identified individual between the South American grounds. The single sample from Chile-Peru had a mtDNA haplotype previously only observed in the Indo-Pacific and had a nuclear genotype that appeared admixed between the Indo-Pacific and South Atlantic, based on genetic clustering and assignment algorithms. The SG samples were clearly South Atlantic, and were more similar to the South American than the South African wintering grounds. This study highlights how international collaborations are critical to provide context for emerging or recovering regions, like the SG feeding ground, as well as those that remain critically endangered, such as Chile-Peru.
... The details of Mysticete breeding cycles vary between species, but in all cases females invest heavily in reproduction. Typically, females gestate for an extended period, typically around 12 months, with lactation thought to be 6-12 months (Lockyer 1984;Best 1994;Burnell 2001). Depending on the species, females might become pregnant while nursing their calf (e.g., minke whales, Balaenoptera acutorostrata) or require a year or two rest period to regain condition before conceiving again (e.g., bowhead, Balaena mysticetus and right whales, Eubalaena spp.). ...
Chapter
GeneticsGeneticsand genomicsEcological genomics tools are providing unprecedented insights into the hidden social lives of baleen whales, from parentageParentage to diet to defining population segments. GeneticGenetics information reveals simple yet critical information about individual whales, from their sex to their age to their kin. Integrating geneticGeneticsand genomicGenomics information with other data such as photo-identification records, stable isotope data on foraging ecology, and hormone studies on reproductive status can provide detailed pictures of individuals and populations. Here we show through published examples how such datasets can be used to provide informationDNA dieton mating systemsMating system and assess population recovery. GeneticGenetics tools such as DNA diet studiesDNA diet study have been instrumental at uncovering new aspects of whale ecology, such as identifying previously unknown prey that are key to the persistence of non-migratory baleen whale populations. Finally, we discuss how geneticsGenetics, acoustics, and cultureCulture interact in whale populations, and how these data are being used in complementary ways to identify units to conserve.
... Where conception specifically occurs remains to be determined. Best (1994) determined that the calving season in South Africa occurs over 118 days around mid-August, with 95.5% of calves being born in this time period. Consideration was therefore given to conduct the annual aerial survey in October being the time of peak calf presence, as most calves would have been born, yet most would not have reached the "critical size" (about 8 m, obtained approximately 2.5 to 3 months after birth) to leave on their annual migration (Best and Rüther, 1992). ...
Technical Report
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Report of the 2018 South African southern right whale aerial survey
... If the latter, the movement of over 1/3 rd of cow-calf pairs away from the South African breeding ground in a two-week time period prior to the assumed peak in cow-calf pair presence seems substantial and warrants deeper investigation. Best (1994) determined that the calving season in South Africa occurs over 118 days around mid-August, with 95.5% of calves being born in this time period. Consideration was therefore given to conduct the annual aerial survey in October being the time of peak calf presence, as most calves would have been born, yet most would not have reached the "critical size" (about 8 m, obtained approximately 2.5 to 3 months after birth) to leave on their annual migration (Best and Rüther, 1992). ...
Technical Report
Full-text available
Report of the 2019 South African southern right whale aerial surveys
... Despite extensive photo-identification work (Rayment WJ, 2018, unpublished data), no female right whale has been seen at the Auckland Islands in the year before giving birth. If the gestation period is about a year, as in SRWs in South Africa [65], the Auckland Islands are not likely to be the principal mating site for SRWs in New Zealand. Further acoustic monitoring and exploration of other areas such as Campbell Island [66] may help locate the main mating habitat for this population. ...
Article
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Autonomous recorders are frequently used for examining vocal behaviour of animals, and are particularly effective in remote habitats. Southern right whales are known to have an extensive acoustic repertoire. A recorder was moored at the isolated sub-Antarctic Auckland Islands for a year to examine whether the acoustic behaviour of southern right whales differed seasonally and throughout the day at their main calving ground in New Zealand. Recordings were made in each month except June, and vocalizations were audible in all months with recordings except January. A total of 35 487 calls were detected, of which upcalls were the most common (11 623). Call rate peaked in August (288+5.9 [s.e.] calls/hour) and July (194+8.3). Vocal behaviour varied diurnally with highest call rates detected at dusk and night, consistent with the concept that upcalls function primarily as contact calls. Zero-inflated model results confirmed that seasonal variation was the most important factor for explaining differences in vocal behaviour. An automated detector designed to expedite the analysis process for North Atlantic right whales correctly identified 80% of upcalls, although false detections were frequent, particularly when call rates were low. This study is the first to attempt year-round monitoring of southern right whale presence in New Zealand.
... In fact, in the present study, the highest fGCm levels were registered in a lactating female that was sighted with two calves (BFA20; Online Resource Fig. S3). Right whales typically give birth to a single calf every 3-5 years after a 12-to 13-month gestation period (Best 1994;Kraus and Hatch 2001), and observations of twin births in right whales (i.e., associated with genetic evidence) are unknown (Best et al. 2015). In the present study, both calves with BFA20 showed normal behaviors and appeared to be in good condition (Best et al. 2015). ...
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In waters off Península Valdés (PV), Argentina, southern right whales (SRW, Eubalaena australis) are occasionally exposed to domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia. Domoic acid toxicity in marine mammals can cause gastrointestinal and neurological clinical signs, alterations in hematologic and endocrine variables, and can be fatal in extreme cases. In this study, we validated an enzyme immunoassay to quantify fecal glucocorticoid metabolites (fGCm) in 16 SRW fecal samples from live and dead stranded whales in PV from 2013 to 2018 and assessed fGCm levels associated with DA exposure. Overall, fGCm levels were significantly lower in SRWs with detectable fecal DA (n = 3) as compared to SRWs with undetectable fecal DA levels (n = 13). The highest fecal DA was observed in a live lactating female, which had low fGCm compared to the other lactating females studied. The highest fGCm was observed in a lactating female with undetectable DA; interestingly, at the time of sample collection, this female was sighted with two calves, an extremely unusual occurrence in this species. Though the sample size of these exceptionally rare breeding-season fecal samples was unavoidably small, our study provides evidence of potential adrenal alterations in whales exposed to an environmental neurotoxin such as DA.
... Males compete with one another for repeated mating opportunities with the focal female in an SAG, and these groups can last for several hours. Courtship activities have been reported year round; this is puzzling, because calving occurs in the winter and gestation is estimated to last 12-13 months (Best 1994). Alternative SAG functions have been proposed and are summarized in Chapter 6. ...
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ABSTRACT Southern right whales (SRW) are capital breeders that use stored energy reserves to sustain themselves and their calves on nursery areas. With successful calving events declining in some SRW populations, it has been hypothesized that nutritional stress in adult females causes reproductive failure or death of calves shortly after birth. Here we compared offsets in carbon and nitrogen isotope values of mothers and their offspring (∆13Ccalf-cow and ∆15Ncalf-cow) among three SRW populations. SRW from Aotearoa New Zealand, with high population growth rates and body conditions scores, have negative ∆13Ccalf-cow suggesting calves are utilizing 13C-depleted lipid carbon in milk to fuel the synthesis of nonessential amino acids used to build new tissues and rapidly grow. In contrast, a significantly positive ∆13Ccalf-cow offset previously reported for SRW from Argentina during a mass die-off event was hypothesized to be due to calves consuming milk with low lipid content. Patterns in ∆15Ncalf-cow were more difficult to interpret and highlight the complexity in nitrogen transfer between mother and offspring. When combined with similar data collected from Brazil and during a low mortality year in Argentina, we hypothesize this approach provides a way to retrospectively compare nutritional condition of breeding adult female SRW across nursery areas. RESUMEN Las ballenas francas australes (BFA) tienen una estrategia de reproducción de “acumulación de capital”, es decir que utilizan las reservas de energía almacenadas para mantenerse a sí mismas y a sus crías en las áreas de cría. Con la disminución de los eventos de partos exitosos en algunas poblaciones de BFA, se ha planteado la hipótesis que el estrés nutricional en las hembras adultas causa fallas reproductivas o la muerte de los ballenatos poco después del nacimiento. En este trabajo comparamos las diferencias en los valores de isótopos de carbono y nitrógeno de las madres y sus crías (∆13Ccría-madre y ∆15Ncría-madre) entre tres poblaciones de BFA. Las BFA de Aotearoa Nueva Zelanda, con altas tasas de crecimiento de la población y altos puntajes de condiciones corporales, tiene ∆13Ccría-madre negativo, lo que sugiere que las crías están utilizando carbono lipídico empobrecido en 13C en la leche para impulsar la síntesis de aminoácidos no esenciales utilizados para construir nuevos tejidos y crecer rápidamente. En contraste, diferencias significativamente positivas de ∆13Ccría-madre reportadas previamente para BFA de Argentina durante un evento de muerte masiva han sido hipotetizadas como debido al consumo de leche con bajo contenido de lípidos. Los patrones de ∆15Ncría-madre fueron más difíciles de interpretar y resaltan la complejidad en la transferencia de nitrógeno entre las madres y sus crías. Al combinar los datos de este estudio con datos similares recopilados en Brasil y durante un año de baja mortalidad en Argentina, podemos plantear la hipótesis de que este enfoque proporciona una forma de comparar retrospectivamente la condición nutricional de las hembras adultas de BFW en distintas áreas de cría. RESUMO A baleia-franca-austral (BFA) possui a estratégia de acumular energia para manter a si mesma e aos seus filhotes nas áreas reprodutivas. Devido a diminuição do número de partos bem sucedidos em algumas populações de BFA, foi sugerida a hipótese de que o estresse nutricional nas fêmeas adultas causaria falhas reprodutivas ou a morte dos filhotes logo após o nascimento. Neste estudo comparamos as diferenças nos valores dos isótopos de carbono e nitrogênio das fêmeas e seus filhotes (∆13Cfilhote-mãe e ∆15Nfilhote-mãe) entre três populações de BFA. As BFA de Aotearoa Nova Zelândia, com altas taxas de crescimento da população e altos valores de condição corporal, têm ∆13Cfilhote-mãe negativo, resultado que sugere que os filhotes estão utilizando carbono lipídico empobrecido em 13C do leite para estimular a síntese de aminoácidos não essenciais utilizados para construir novos tecidos e crescer rapidamente. Por outro lado, as diferenças significativas positivas de ∆13Cfilhote-mãe reportadas previamente para BFA de Argentina, durante um evento de mortalidade em massa, foram atribuídas ao consumo de leite de baixo conteúdo de lipídios. Os padrões de ∆15Nfilhote-mãe foram mais difíceis de se interpretar e demonstraram a complexidade na transferência de nitrogênio entre as mães e seus filhotes. Ao combinar os dados deste estudo com dados similares coletados no Brasil e durante um ano de baixa mortalidade na Argentina, sugere-se que os estudos isotópicos seriam uma forma de comparar retrospectivamente a condição nutricional das fêmeas de BFA em distintas áreas reprodutivas.
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Of key importance for the comprehension of humpback whales’ (Megaptera novaeangliae) distribution patterns and habitat use is to quantify how ecological and environmental factors affect the distribution of animals, which requires knowledge on dispersal movements of individuals. Using an opportunistic sightings dataset collected in the Sainte Marie Channel (Northeast of Madagascar) and satellite telemetry data acquired for this study (25 tagged whales), the aim of this thesis was to study the movements and the habitat use of humpback whales in Madagascar during the breeding season, according to sex and reproductive status. Physiographic and oceanographic variables (measured by satellite) were extracted under each position. A general distribution pattern of habitat use during the breeding season was also proposed based on additional humpback whales tracks from others breeding grounds of the Southern Hemisphere: Brazil (n=81 individuals), the Western Australian coast (n=26), and the Eastern Australian coast (n=11). In the Sainte-Marie Channel, groups without calves dominated the first 30 days of the breeding season, followed by an increase in groups with calves (Chapter III). Water depth influenced the distribution of social groups with mother-calf pairs more frequently found in relatively shallow water (0-20 m). Along the coast of Madagascar, over the shelf, females showed localized behavior in deep water and at large distances from shore suggesting that their breeding habitat extends beyond the shallow coastal waters (Chapter IV). Males’ active swimming speed decreased in shallow waters, but we found no influence of environmental parameters on males’ movements. In oceanic habitats, both males and females showed localized behaviors in shallow waters and high surface chlorophyll-a concentrations. The active swimming speed accounts for a large proportion of the whale observed speed while observed direction of tagged whales tending to be closer to the current direction when the current intensity was high. Our comparative study between breeding areas showed that the spatial distribution varies according to the period of the season, between the studied sites, sex and breeding status (Chapter V). Early and late in the season, males moved more directly and in more offshore areas than females, especially females with calves. At the peak of the season, both males and females performed more localized movements than at the other periods. Accounting for differences in the spatio-temporal variability of the distribution of males and females in the breeding grounds seems a necessity to better understand the humpback whales ecology and contribute to the species conservation.
Chapter
Right whales have a long history of interactions with humans, being arguably the first commercially hunted species of whale. There are currently three recognized species of right whales including the North Pacific right whale (Eubalaena japonica)Eubalaena japonica, the North Atlantic right whale (Eubalaena glacialis)Eubalaena glacialis, and the southern right whale (Eubalaena australis)Eubalaena australis. The conservation status of these three species varies. Both of the northern hemisphere species are endangered and have only a few hundred individuals remaining, while the southern hemisphere species have multiple growing breeding populations that include thousands of individuals. Studies of right whale behavioral ecology and acoustic communication started in the 1960s and 1970s with studies off Massachusetts for North Atlantic right whales, and off ArgentinaArgentina for southern right whales. Behavioral studies of the less accessible North Pacific right whales have lagged behind, with most information on their behavior being published in the past 20 years. All right whale species share similarities in their acoustic repertoires, with a stereotyped contact callContact call, the upcallUpcall and a loud broadband impulsive sound, the gunshotGunshot, being described for all species. Beyond these stereotyped sound types, right whales all share a graded repertoire of signals that range from pulsive to tonal in structure. Sound type usage varies by the behavioral context of the communication, and sound types appear to serve similar behavioral roles in all three species. Studies across species suggest that there are differences in sound production that reflect the sex and age class of the signaling individual. Additional studies have demonstrated behavioral responses of right whales to exposure from noise in their environments. Emerging areas for future research include the expansion of the use of passive acoustic monitoring to aid in the conservation of these whales.
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This chapter examines the characteristics, distribution, and behavior and conservation status of the right whale. There has been disagreement on two questions of balaenid systematics and nomenclature-concerning the number of extant species of right whales and whether or not bowhead whales and right whales are congeneric. They have an extremely robust body form, bordering on rotund, with thick blubber layer and the girth at times exceeding 60% of total body length. The body is mostly black, sometimes with irregular white ventral patches. Right whales are found in the middle latitudes of both the Northern and the Southern hemispheres. There are three geographically isolated populations currently recognized as separate species: in the North Atlantic, North Pacific, and Southern oceans. Right whales feed entirely on zooplankton, especially on large calanoid copepods. At times they also feed on smaller copepods, krill (larger shrimp-like crustaceans), pteropods (tiny planktonic snails), or the planktonic larval stages of barnacles and other crustaceans. They migrate annually between high-latitude feeding grounds and low-latitude calving and breeding grounds. Calving in right whales occurs during winter. Where the calving grounds are known, they are in shallow coastal regions or bays. The only known current calving ground in the western North Atlantic is in coastal waters near Georgia and northeastern Florida. Right whales are observed to frequently perform highly energetic behaviors at or above the surface of the water. These aerial behaviors include breaching, lobtailing, and flippering. North Atlantic right whales were the first whales to be harvested commercially by the Basques along the Atlantic coast of Western Europe as early as the eleventh century. The whales were killed primarily for oil, which was sold across Europe, as the technology of the time did not permit preservation and widespread transportation of meat.
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The mating pattern is usually monogamous, with less social schooling of the type common to many Odontoceti. Formation of loose aggregations occurs during migration and seasonally. Geographical segregation of sexes, sexual classes and age classes sometimes occurs, eg in Balaenoptera acutorostrata; this can seriously bias the sex ratio and age distribution of catches. In small and greatly reduced stocks such catches can seriously alter the population structure. The female reproductive cycle is generally 2 yr, with a gestation period of c1 yr. Lactation lasts c0.5 yr. Normally just 1 calf is born in warm temperate or sub-tropical waters. Most baleen whales undertake extensive migrations for feeding, an exception being Balaena mysticetus. The reproductive cycle appears to be geared to this annual cycle of migration and feeding. Baleen whales feed mainly by filtering small swarming planktonic Crustacea, the production of which is greatest in cold high latitude waters. Baleen whales thus need to leave the home breeding grounds for the high latitude seas each spring in order to feed and store energy in the form of fat as reserves for the months of poor feeding. Even Eschrichtius robustus, a bottom-feeder, undertakes such migrations. Weaning in most species occurs during or after the summer feeding season. The success of factors such as fertility, pregnancy, lactation, developmental growth and sexual maturity, and net recruitment are dependent on efficient storage of energy for body maintenance, foetal growth and milk production. Inter-correlation between history of exploitation, pregnancy rates and individual growth rate and the attainment of sexual maturity is discussed in relation to possible changes in food supply. -from Author
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This study is based on data from several thousand specimens of spotted porpoise, Stenelfa attenuata, incidentally killed in the purse seine fishery for yellowfin tuna, Thunnus albacares. Average length at, birth is 82.5 em. Gestation is 11.5 mo. Average length at 1 yr is 138 em. Length-weight equations are given for fetuses and postnatal males and females. Age was estimated from dentinal layers in thin sections of teeth. A two-phase Laird-Gompertz growth model was fitted to the layer-length data. Direct calibration of the dentinal layers beyond the first year (two layers) was not possible, and three alternative hypotheses were considered: 1) two layers per year, until pulp cavity occluded, 2) two layers per year in first year, and one per year thereafter, and 3) two layers per year until puberty, and one per year thereafter. The second alternative is most probably the correct one, but reproductive parameters were estimated in terms of layers. Breeding is diffusely seasonal, with prolonged calving seasons in spring and fall and a pronounced low in winter. A third calving season may exist in the summer. Average age at attainment ofsexual maturity of males is approximately 12 layers (average length about 195 em and average weight about 75 kg). Females attain sexual maturity on the average at about 9 layers and 181 em. Ovarian changes in adult females are described. Apparently postreproductive females were encountered in the samples. It is concluded that corpora albicantia of ovulation and pregnancy persist indefinitely in the ovaries. It was not possible to distinguish between the two types of corpora. Ovulation rate changes with age, from about four per layer in very young adult females, to about one per layer in older females. The average calving interval is 26 mo long and consists of 11.5 mo of pregnancy, 11.2 mo of lactation, and 3.3 mo ofresting and/or estrus. About 9.6% of lactating females are also pregnant. Pregnancy rate decreases with age, from about 0.6 per year at 8 to 10 layers, to about 0.3 at 16 layers. The overall sample contained 44.9% males and 55.1% females. Sex ratio changes with age, from near parity at birth, indicating higher mortality rates for males. Gross annual production of calves, based on age and sex structures of the sample and the estimated pregnancy rate, is 14.4% of the population per year. No evidence was found of age or sex segregation in schooling. The estimated parameters differ in a consistent way from those estimated for a population of Stenella attenuata in the western Pacific, possibly reflecting the exploitation in the eastern Pacific.
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Since 1979, 245 right whales (excluding calves) have been individually identified in aerial photographs taken annually on the South African coast, using variations in dorsal pigmentation and callosity patterns. White or grey blazes (or both) occurred dorsally in 16,7% of individuals, one form of which (partial albinism) occurred in 3,6% of the calves born but may be sex linked. In 19 animals carrying dorsal marks that were resighted two to seven years later, changes in the appearance of the callosities were noted in 95% of individuals, 58% showing pronounced changes. Definite matches between years were made for 139 cows with calves. The average per capita calving interval, adjusted for incomplete spatial and temporal coverage, was 3,183 ± 0,091 (SD) years, or a calf production rate of 0,314 ± 0,009 (SD) per adult female per year. From a simple model it is shown that rates of population increase as high as that observed (6–7%) can only be maintained with a calf production rate of this order if the age at first parturition is relatively low and/or the adult survival rate high.Sedert 1979 is 245 suidelike noordkapers (kalwers uitgesluit) op grond van variasie in dorsale pigmentasie en velgroeiselpatrone afsonderlik geïdentifiseer op lugfoto’s wat jaarliks aan die Suid-Afrikaanse kus geneem is. Dorsaalgelee wit of grys vlekke (of albei) kom op 16,7% van die indiwidue voor. Een vorm (gedeeltelike albinisme) wat op 3,6% van die kalwers voorgekom het, mag geslagsgekoppel wees. Van die 19 diere met dorsale merke wat na twee tot sewe jaar weer waargeneem is, het 95% veranderinge in die voorkoms van die veluitgroeisels getoon. Hiervan het 58% sterk verandering ondergaan. Positiewe identifikasie van 139 koeien-kalfpare op ’n meerjarige grondslag is gemaak. Die gemiddelde kalfinterval per capita, aangepas by die onvolledige dekking m.b.t. ruimte en tyd was 3,183 ± 0,091 (standaardafwyking) jare of ’n kalfproduksietem-po van 0,314 ± 0,009 (standaardafwyking) per volwasse koei per jaar. Met behulp van ’n eenvoudige model word aangetoon dat so ’n hoë aanwastempo (6–7%) in ’n populasie slegs met bogenoemde kalfproduksie-tempo volgehou kan word indien die ouderdom van die koeie by die geboorte van hul eerste kalf redelik laag is en/of die kans op oorlewing van die volwassenes hoog is.
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Since 1970, southern right whales have been studied on their winter/spring aggregation areas in protected waters near the coast of Peninsula Valdes, Argentina. Many individuals return to the area each year, but mature females tend to be seen only in years when they give birth (usually every 3rd year); 74 of the known females have had >2 calves, with a mean calving interval of 3.7+ or -1.25 yr. Age of first calving for 2 females was 7 yr. Mothers with young calves are usually positioned along the coast in water c5 m deep. Right whales are found at Peninsula Valdes in three separate areas: 1) predominantly occupied by mothers and calves, 2) predominantly occupied by males and mature females in non-calf years, and 3) occupied by all categories of whales including subadults and mating groups. -from Author
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Desirable external measurements are defined, and important natural history data relating to reproduction, food habits and parasites are listed, in an attempt to standardize the recording of this vital information for use both by cetologists and by zoologists lacking previous experience with the smaller cetaceans.
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Observations on the increase of ovarian weight in the female humpback whale cover stages from late foetal life until after the attainment of sexual maturity. Variations in ovary weight during different phases of the reproductive cycle are recorded. Graafian follicles up to 0.13 mm in diameter have been found in the foetal ovary just prior to birth. These initially develop until from 11 to 29 mm (median value 20 mm) in diameter when the female reaches the maturing length range. At sexual maturity one of these follicles enlarges, exceeding 30 mm in diameter before rupture. After ovulation a corpus luteum is rapidly formed and if conception has taken place, this gland enlarges and remains active until parturition. After parturition there is rapid resorption of the corpus luteum to form a corpus albicans. Variations in the sizes and weights of functional corpora lutea are discussed. There is considerable reduction in the diameters of Graafian follicles in late pregnancy to a median value of 6 mm. After parturition follicles enlarge so that in the ovaries of females in late lactation the largest follicles once more range from 11 to 29 mm in diameter with a median value of 20 mm. In an ovulatory period of from June to November the maximum frequency of ovulations is in late July, though considerable numbers occur in August and September. On the availabIe evidence most female humpback whales ovulate only once in their ovulatory period, a few ovulate twice, and extremely few three times.
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The purposes of this review are to describe and critique methods used to estimate reproductive parameters. to summarize estimates in the literature and to examine patterns in the estimates and their implications. Reviewed are gestation period, fetal growth rate, size at birth. size and age at attainment of sexual maturity. average size and age of adults, maximum size, asymptotic length, ovulation rate, pregnancy rate, calving interval, length of lactation, weaning age. length of "resting" period, age and sex structure, and birth rates. Also discussed are the effects on the estimates of seasonality, schooling segregation. geographical variation and exploitation and the relationships between parameters.
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Between September 1984 and January 1993, monthly counts of southern right whales were made from up to four vantage points in the De Hoop Nature Reserve, South Africa. Evidence from aerial surveys indicates that these vantage points are well situated in relation to the main concentration of right whales off De Hoop. Right whales arrive in June, reach peak abundance in September and depart in December or January. The incidence of calves increases from zero in June to 15-22% between August and October (reflecting the season of births), before increasing again to 33% in November and 42% in December (reflecting the earlier departure of animals without calves). The numbers of right whales seen off De Hoop on aerial surveys from 1971 to 1992 have increased at a rate faster than that of the inshore population as a whole, indicating a degree of net immigration into the area. The rate of this immigration may have slowed down during the past 10 years. Shore counts for adults show a positive correlation with aerial counts in the same year, confirming their utility in monitoring future trends in abundance.
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Between July or August and November 1988 and 1989, 72 cow-calf pairs of right whales (Eubalaena australis) were measured photogrammetrically from the air off De Hoop, South Africa. Median coefficients of variation ranged from 1.29 to 4.56%, being lowest in cows and calves for measurements of total length. Fifty-seven adult cows measured from 12.37 to 15.54 m in length, with females photographed for the first time with a calf (= primiparous) being smaller than females that had been seen for the first time with a calf at least five years previously. The lengths of 72 calves ranged from 4.53 to 9.24 m, with those from primiparous females being significantly smaller than calves of multiparous females in every month except July. For 37 calves photographed on more than one occasion the growth rate averaged 2.8±0.7 cm per day, with no significant difference between growth rates of calves from primiparous and from other females, and no significant decrease in growth rate between July/September and September/November. Calves grew from an average of 40% of their mother's length in late July to 51% by mid-October. The size distribution of the adult females was no different from that of 25 adult females landed at South African whaling stations between 1911 and 1963 (after adjustment for possible differences in measurement techniques). Five near-term foetuses recovered in June-August in the same whaling operations also agree closely with the size of calves predicted for 1 August. In a comparison with 17 calves stranded or dying accidentally on the South African coast, most of the accidentally caught animals agreed closely in size with the sample of photogrammetrically measured animals, while most of the stranded animals were equal to or smaller in size than the smallest length interval in the photogrammetrically measured animals. The calves of primiparous females may therefore suffer a higher natural mortality rate than those of multiparous females.
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Tissue 13C of bowhead whale, Balaena mysticetus, varies seasonally in response to geographic variations in the 13C of prey organisms consumed along the annual migratory route between the Bering, Chukchi and Beaufort Seas. Seasonal changes in body 13C of whales taken in 1986 from Alaskan waters provide a means of estimating energy intake from the different habitats in which the whales feed. Adult bowheads do not show significant seasonal shifts in the 13C of muscle and visceral fat. Their enrichment in 13C relative to subadult whales suggests that they acquire most of their food from fall and winter feeding or from unsampled parts of the summer range where zooplankton are enriched in 13C. Young individuals however, undergo marked seasonal shifts indicating that they feed heavily both in the summer and autumn or winter. Oscillations in 13C along the length of the baleen also provide a measure of age. Baleen growth rates decline as the whales age and provide a means of correcting for wear loss and allow aging of individuals less than 12 yr old. Although body length is a poor indicator of age in young bowhead whales, baleen length is closely correlated. Growth rates of bowheads after Year 1 are slow ( 0.4m yr-1) and up to 20 yr are required to reach the assumed length of sexual maturity at 13 to 14m.
Methodology for behavioural studies of cetaceans: right whale mother‐infant behaviour
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