ACS Research Committee Report

Saving the Vaquita
Source: Jaramillo-Legorreta, A., Rojas- Bracho, L., Brownell, R.L., Read, A.J., Reeves, R.R., Ralls, K., and Taylor, B.L. 2007. Saving the vaquita: immediate action, not more data. Cons. Biol. 21 (6): 1653-1655.

Data were collected off Central America during winter 2001 to 2004 and off the Antarctic Peninsula during summer 1981 to 2004. Photographs were compared to identify individuals common to both regions.

The Baiji, the Chinese river dolphin, has been declared biologically extinct, making the vaquita, the Gulf of California porpoise, the most endangered of any cetacean.

Bycatch in fisheries is the primary threat to the survival of the vaquita. The authors of this study used a model of current population and estimated bycatch rates to determine the current vaquita population and to hypothesize on the best course of action for this species.

There are three primary fishing villages, El Golfo de Santa Clara, San Felipe, and Puerto Penasco, in the Gulf of California.

Between 1993 and 1994, El Golfo de Santa Clara had an estimated bycatch of 39 vaquitas per year; San Felipe was assumed to be comparable to this village. The third village, Puerto Penasco, was reported to have little if any bycatch because fishermen do not work in areas inhabited by vaquitas. Therefore, a reasonable minimum estimate of bycatch is 78 vaquitas per year.

A survey in 1997 estimated 567 vaquitas were present in the Gulf of California. This population estimate was corrected for the number of births and deaths per year since that time, resulting in a current population estimate of 150 vaquita.

A threshold for an effective reproductive population is estimated at 50 animals. Only half of the animals in the population at any time would be considered adults, which means the overall population size must be about 100 to be at threshold. Therefore, it is estimated that vaquitas will be at threshold in only two years.

The authors claim that any increase or decrease in such a small population will be difficult to detect; therefore, they suggest that there is no need for further population estimates of the species. For the current population, a growth rate of 4%, which is a maximum estimated rate of increase, would result in only eight new vaquitas each year, meaning that mortality must be less than eight animals per year to maintain the population size.

The authors therefore suggest that the only viable solution to protect this species is a complete moratorium on all fishing gear that entangles vaquita. Conservation funds could be best put to use through a buyout or similar program that would compensate fisherman. Only through drastic, cooperative multinational efforts will the vaquita be saved.  

Patterns of Male Reproductive Success in North Atlantic Right Whales
Source: Frasier, T.R., Hamilton, P.K., Brown, M.W., Conger, L.A., Knowlton, A.R., Marx, M.K., Slay, C.K., Kraus, S.D., and White, B.N. 2007. Patterns of male reproductive success in a highly promiscuous whale species: the endangered North Atlantic right whale. Molecular Ecol. 16: 5277-5293.

Male North Atlantic right whales have extreme physiological reproductive adaptations, but their mating patterns are not well understood. Right whales grow to lengths over 17 m; males have penises that reach approximately 2.3 m and testicles that have a combined weight of approximately 972 kg. These are the largest testes of any mammal and the highest testes weight to body weight ratio and penis length to body length ratio of any baleen whale. These adaptations suggest that this species engages in sperm competition.

Reproductive behavior in right whales is usually associated with surface active groups (SAGs) in which many males aggregate around one female. The female calls to attract males to the SAG and she turns upside down to make mating difficult. This behavior results in males actively competing for access to the female, thereby presumably ensuring that the strongest males will gain the mating opportunities.

Documented SAGs last an average of one hour; females roll over to breath approximately once every minute. If copulation takes place each time she rolls over, then she can mate on average 60 times during a SAG. Therefore, the female reproductive tract is the arena for sperm competition from multiple male north Atlantic right whales.

This study uses genetics and photo-identification to determine the patterns of male reproductive success. A total of 278 individuals, including 127 females and 151 males, were genotyped at 28 loci. These samples represent about 63% of all whales photo-identified from 20 years of research through 2001 and 74% of all whales alive in 2001. Eighty-seven (35%) mother/calf pairs and 116 (69%) candidate males were sampled.

Candidate males were defined as males that were five or more years old at time of sampling; this is a conservative estimate, because most researchers assume males reach maturity at the same time as females, which is at about eight years. Twenty-six males were assigned paternity for 36 calves, resulting in an average of 1.38 calves per male (similar results were found with several different paternity analyses). More males fathered more than one calf than expected, indicating that mating is not random.

This same analysis was conducted with males that were 10 years and older, but the results were similar. No males under the age of 10 were assigned paternity in any analysis.

Only 51% of sampled calves were assigned paternity, even though 69% of all males were sampled. Therefore, 49% of calves were fathered by males that were not sampled. This represents significantly fewer paternities than expected. There are two possible explanations: a) there are a small number of non-sampled males that are very successful and account for all the missing paternities or b) that the population size of right whales is larger than currently estimated (300-350 animals).

The results of one paternity analysis suggests that the paternity of calves fathered by non-sampled males has a similar pattern as for those of sampled males. This result rejects the explanation that there are a small number of very successful males that have not been sampled and suggests that there is actually a larger population than currently estimated.

One of the factors affecting the number of mates for each male is the synchrony of ovulation in females; females that are asynchronous provide an opportunity for males to compete for multiple mates within a season.

Right whales have a common calving season, but calving dates range throughout a span of several months. These data suggest that female ovulation may be asynchronous.

However, out of all paternities, only one male fathered more than one calf in a single year. The average inter-calf interval was 5.7 years, reinforcing that there aren’t a few number of males with significantly higher reproductive success. There was only one case of the same pair mating more than once, suggesting that right whales are promiscuous.

Paternities were biased towards older males; most males did not father a calf until they were 15 years old, which is almost twice the age of first fertilization in females. Most likely, younger males are physiologically able to sire offspring around the same age as females, but an aspect of mate competition prevents younger males from reproducing.

Males do not change significantly in size after the age of 10, so this is likely not a factor in mating success and there are no other external features that seem to make males more successful with age.

Two possible explanations for this age discrepancy are that a) there is a learned aspect to mating or b) older males have increased testes development.

SAGs are often seen on the feeding grounds during summer and fall, but calving dates indicate that mating doesn’t actually occur until the winter. These earlier SAGs may represent “practice” opportunities for males.

These mating patterns mean that genetic material is not being passed on to calves equally from the population, which in a critically endangered species such as the right whale can increase problems associated with inbreeding in a reduced population size.

However, the presence of a potentially significant number of non-sampled males that are reproductively successful is an optimistic sign that this population is actually larger than currently estimated.  

Fin Whale Feeding Dynamics
Source: Goldbogen, J.A., Pyenson, N.D., and Shadwick, R.E. 2007. Big gulps require high drag for fin whale lunge feeding. Marine Ecol. Progress Series 349: 289-301.

Baleen whales engage in three distinct feeding styles: a) benthic suction feeding (gray whales), b) skim feeding (right and bowhead whales), and c) lunge feeding (fin, blue, minke, and humpback whales).

Lunge feeding involves engulfing large quantities of water and prey and filtering the prey out of the water using baleen plates. Lunge feeders have ventral throat grooves that expand to accommodate the water and prey. In addition, they have large, unfused mandibles (lower jaw bones) that make up almost a quarter of the body length. The mandibles can rotate during lunge feeding to increase the area of the mouth exposed in order to take a larger mouthful of water and prey.

Fin whales use this strategy during feeding. They are very streamlined whales capable of swimming at high speed; however, when they take a mouthful of water and expand the throat grooves, this streamlined profile is lost. It therefore has been hypothesized that feeding has a high energetic cost by creating drag.

Recent tagging efforts have shown that fin whales routinely lunge several times per dive at depths greater than 200 m. Each lunge involves a rapid deceleration of the whale despite continued swimming.

It has been suggested that the energetic cost of lunging is a constraint on the dive time and increases the post-dive recovery period for these animals. In fact, skim feeding whales of similar size can dive approximately twice as long as lunge feeders.

This study uses models based on data from digital tags and morphological characteristics of fin whales to estimate the costs and benefits of lunge feeding. Tagging has shown that each lunge lasts approximately 3 s; the mouth opens at the maximum velocity and maximum deceleration (and maximum drag) occurs at the moment of maximum mouth gape. The high drag produced at the point of maximum gape serves to expand the ventral grooves. The streamlined shape of the body allows for the mandibles themselves not to experience significant drag during a gape, but rather that drag will be focused on the ventral grooves causing them to expand. The mandibles can lower to an angle of 80° during a lunge. When taking into account this gape angle, the length of the mandibles (4.6m), and the duration of the lunge, the average engulfment volume is calculated as 71 m³.

A fin whale can take in an average of 11 kg of krill per lunge; therefore, a fin whale would have to execute approximately 83 lunges per day to fulfill its energy requirements. This energetic demand can be met by an average of 21 dives over approximately 3 hours.

If lunge feeding whales are able to control the gape angle, then the magnitude of the volume engulfed would also be under voluntary control. Lunge feeders should then be able to take smaller gulps at lower costs if dealing with smaller aggregations of prey.

Lunge feeders may also increase lunge speed to capture more agile prey. The selective advantages of lunge feeding, such as the large engulfment capacity, must outweigh the energetic costs of this feeding technique.  

Baleen Whales Are Not an Important Prey for Killer Whales in High Latitudes
Source: Mehta, A.V., Allen, J.M., Constantine, R., Garrigue, C., Jann, B., Jenner, C., Marx, M.K., Matkin, C.O., Mattila, D.K., Minton, G., Mizroch, S.A., Olavarria, C., Robbins, J., Russell, K.G., Seton, R.E., Steiger, G.H., Vikingsson, G.A., Wade, P.R., Witteveen, B.H., and Clapham, P.J. 2007. Baleen whales are not important as prey for killer whales Orcinus orca in high-latitude regions. Marine Ecol. Progress Series 348: 297-307.

Killer whales are well documented to have at least three ecotypes: residents (fish eating), offshores (likely fish eating), and transients (marine mammal eating).

It has been a subject of recent debate whether large whales constitute a large portion of the transient killer whale diet. Scientists have hypothesized that killer whale predation pressure is the primary reason that baleen whales undergo extensive migrations from high latitudes in summer and low latitudes in winter.

However, this hypothesis has been questioned by other scientists who believe that killer whale predation is uncommon in high latitude regions. They state that whales which have scars from killer whale attacks acquire them in their first migration, prior to arriving in high latitudes.

In a review of interactions between killer whales and other marine mammals, 111 reports of killer whale aggression towards large whales were found over a 160 year period. Few large whales were actually killed during these incidents. Minke whales, one of the smallest baleen whales, may be attacked by killer whales more often than their larger counterparts.

One scientist suggested that the depletion of whale populations due to hunting may have forced killer whales to switch their preferred prey source from large whales to smaller marine mammals. This hypothesis is based primary on the idea that killer whales attack large baleen whales regularly enough that the loss of this prey would cause a prey switch.

Evidence of killer whales killing large whales in high latitudes is minimal. Review of photographs of humpback whales off eastern Australia found that most whales with killer whale scars had them at their first sighting and did not acquire more throughout life. Attacks on gray whales off the California coast are primarily focused on calves during the northbound migration.

This study examined photographs from three baleen whale species (humpback, blue, and pygmy blue whales) in 24 regions worldwide to a) determine the proportion of whales that have scars from killer whale attacks, b) identify whether these scars were present at the first sighting or were acquired later in life, and c) define the severity of any scarring (mild, moderate, or severe).

The proportion of whales with rake (tooth) marks ranged from 0 to >40% in the different populations. As examples, 9.9-11% of Gulf of Maine humpback whales, 17.7% of humpback whales in Hawaii, and 42.1% of blue whales in Western Australia had rake marks. The highest proportion of whales with rake marks (and highest proportion of whales with severe scarring) was humpback whales in Mexico. Most animals with rake marks had only mild severity.

Multi-year resightings were only available in three of the humpback whale populations: Gulf of Maine, Greenland, and Mexico. Of these 86.3-100% had the scars at the time of first sighting. In the North Atlantic, rake mark frequencies ranged from 8.1% near Norway to 22.1% near Greenland.

Almost all of the whales in the North Atlantic share the same breeding grounds in the Caribbean. The difference in rake marks among feeding areas and the prevalence of scars being present at first sighting indicate that migrating humpback whale mother/calf pairs are subject to different levels of predation depending on their destination.

This analysis indicates that adult whales face little predation risk from killer whales. The fact that the majority of documented scars were only mild in severity may mean that a) attacks resulting in severe damage are more often fatal, or b) attacks resulting in severe damage are rare.

These data suggest that killer whales may occasionally take an adult large whale, but large whales do not represent a significant prey source. Therefore, it is unlikely that killer whales were forced to switch prey due to a post-whaling reduction in population size of large whales.  

Managing Wildlife-based Tourism
Source: Higham, J.E.S. and Bejder, L. 2008. Managing wildlife-based tourism: edging slowly towards sustainability? Current Issues in Tourism 11(1): 75-83.

Eco-tourism may contribute to conservation goals, but unfortunately often symbiosis between the two is the exception rather than the rule. This is especially the case with wildlife-based tourism. This issue is apparent at Monkey Mia in Shark Bay, Australia where there is a population of dolphins that is the focus of visits from over 100,000 people annually.

Since the 1960s, several dolphins have been hand-fed by humans at a beach in Monkey Mia. Currently, five adult female dolphins are still hand-fed by tourists. In addition, vessel-based dolphin watching occurs in the Bay near Monkey Mia. One commercial operator has been active since 1993 and another was added in 1998.

When the second commercial dolphin watch operator was added, the Department of Conservation and Land Management (CALM) started a program to monitor the potential impacts of these activities on the resident dolphins. The licenses granted to the vessel operators were contingent on the results of these studies.

The dolphins of Shark Bay are a unique case in that there are data from before and during vessel-based dolphin watching. In addition, there are data from not only the Monkey Mia site, but also from a neighboring area where there is no tourism activity. This unique situation provides two controls for the study of impacts on dolphin behavior and distribution.

When comparing the period before vessel-based tourism and the period when only one operator was active, there was no change in dolphin abundance. However, after the second operator began its dolphin-watching, there was a significant average decline in abundance of 14.9%. At the same time, there was a non-significant average increase of 8.5% in the control (non-tourism) site.

The local decline was not part of an overall decline or due to ecological factors, because either possibility would have similarly affected the control site.

When faced with these results of the monitoring program, CALM and the Marine Parks and Reserves Authority decided to reduce the number of commercial dolphin-watching licenses from two to one and introduce a moratorium on any increase in research vessel activity.

If the findings of this study can be extrapolated to other marine mammal populations that are subject to whale watching activity, one might conclude that cetacean-based tourism perhaps has a larger impact on the animals than previously thought. Most populations and areas do not have control data like that in Shark Bay to evaluate possible impacts; therefore, impacts may go unnoticed. The management decision made in Shark Bay, and similar decisions that are now occurring in other areas of the world, may indicate that there is a paradigm shift in conservation strategies for marine mammals.  

   

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