Abstracts

The reproductive ecology of resident manta rays
(Manta alfredi) off Maui, Hawaii, with an emphasis
on body size

Deakos, M. H. (2011) Environmental Biology of Fishes In Press

Abstract
In resident manta rays (Manta alfredi) off Maui, sexual maturity appears delayed until growth exceeds 90% of maximum size, an indicator that large body size provides a reproductive advantage at the expense of a shorter reproductive time period. In this study, 286 surveys were conducted between 2005 and
2010 using photo-identification and photogrammetry to study the reproductive ecology of a resident population of manta rays off Maui, Hawaii, and
investigate the reproductive benefits of large body size in each sex. Although reproductive activities occurred year-round, mating trains and late-term pregnant females were significantly more likely to be observed during the winter months. Some females were pursued by males during both winter and summer of the same year, suggesting multiple ovulations may be possible in a single year. Males
likely detect a female's reproductive state by positioning directly behind her, or passing through her bodily excretions. The mean pregnancy rate was estimated at 0.56 pregnancies/adult female/year with larger females pregnant more often, and more likely in consecutive years. The operational sex ratio was heavily skewed with 2.68 adult males per reproductively available female. Although males appear to compete with one another for females within a mating train, no
direct physical competition was ever observed between males. Evidence of highly dynamic mating trains lasting more than one day suggests endurance rivalry may be the primary mating strategy among males, during which larger males may benefit from greater energy reserves. The study area appears to be an important staging area for mating individuals in this population.

Characteristics of a manta ray Manta alfredi population off Maui, Hawaii, and implications for management

Deakos, M. H., Baker, J.D., Bejder, L. (2011) Marine Ecology Progress Series 429:245-260

Abstract
Late maturity, few offspring and a residential nature are typical characteristics of Manta alfredi that make this species vulnerable to localized anthropogenic threats. Improving its life history information is crucial for successful management. A total of 229 surveys was conducted from 2005 to 2009 at a manta ray aggregation site off Maui, Hawaii, to qualitatively and quantitatively describe the abundance, movements and temporal habits of this population. Photo-identifications revealed 290 unique individuals, but a discovery curve showed no asymptotic trend, indicating that the number of individuals using the area was much larger. Resightings and manta ray follows revealed that this population and a population off the Big Island may be independent, island-associated stocks. High resighting rates within and across years provided strong evidence of site fidelity. Findings were consistent with a population of manta rays moving into and out of the Maui aggregation area, with a varying portion of the total population temporarily resident at any given time. Males, accounting for 53% of all individuals, resided for shorter periods than females around the study area. Manta rays were usually absent at first light with numbers increasing throughout the day. More frequent mating trains were observed during the winter months. Shark predation was evident in 33% of individuals, and 10% had an amputated or non-functional cephalic fin. This small, demographically independent population appears vulnerable to the impacts from non-target fisheries, primarily from entanglement in fishing line, and could suffer from exploitation by commercial ‘unregulated, swim-with manta ray’ programs. Management on an island-area basis is recommended.

The ecology and social behavior of a resident manta ray (Manta alfredi) population off Maui, Hawaii

Deakos, M. H.
Published Doctoral Thesis, University of Hawaii at Manoa, 2010

Abstract
Findings from this study broaden our understanding of the ecology and behavior of Manta alfredi. Paired-laser photogrammetry, photo-identification, and active tracking were used to investigate a Manta alfredi population off Maui, Hawai‘i. A total of 286 surveys were conducted between 2005 and 2010, resulting in 309 different individual manta rays, of which 163 were sized. A discovery curve showed no asymptotic trend, indicating the number of individuals using the area was much larger than the total identified. Resights and manta follows revealed a minimum home range spanning the four-islands within Maui County with high site fidelity to the study area within and across years by most individuals. There was no evidence of movements to the Big Island, suggesting there are two independent, island-associated stocks. Males, accounting for 51% of the population, were estimated to reach sexual maturity at 2.8 m disc width ( DW) and females at 3.37 m DW. Maximum sizes were much smaller than those reported in other parts of the world indicating geographic variation in size for this species. The mean pregnancy rate was estimated at 0.56 pregnancies/female/year with larger females pregnant more often and more likely in consecutive years. Significantly more mating trains and pregnant females occurred during the winter season. No direct physical competition was observed between males but evidence of mating trains lasting more than one day suggests endurance rivalry, during which larger males may benefit due to greater energy reserves. The absence of individuals less than 2.5 m DW suggests age class segregation is occurring in this population. Shark scars were evident in 24% of individuals and 10% had an amputated or non-functional cephalic fin, likely caused by entanglement in monofilament fishing line. The Maui aggregation site appears to be an important staging area for breeding and parasite removal by members of this population. Late maturity, low fecundity, and the residential nature of individuals in this population make them particularly vulnerable to localized, anthropogenic threats. Implementing successful management practices to reduce the threat of entanglement and of unregulated “swim-with manta ray” programs is recommended.

Paired-laser photogrammetry as a simple and accurate system for measuring the body size of free-ranging manta rays Manta alfredi. Aquatic Biology 10:1-10

Deakos M. H. (2010) Aquatic Biology 10:1-10

Abstract
Morphometrics are useful for describing and managing animal populations, but measurements can be difficult to obtain, especially on large free-ranging aquatic animals. The accuracy and precision of paired-laser photogrammetry were tested as a simple and non-invasive remote sensing system for measuring the body size of free-ranging, resident manta rays Manta alfredi, a newly described species that is poorly understood. Based on repeated measurements of a pipe of known size, the paired-laser system proved accurate (mean error of 0.39%) and precise (CV = 0.54%). Repeated measurements on 154 different manta rays visiting a cleaning station off Maui, Hawaii, produced a mean CV of 1.46%. Disc length (DL) measurements were more precise than disc width (DW) measurements, and an empirically derived disc ratio (DR) function was applied to convert DL to DW measurements for standard comparison with other studies. Sexual dimorphism was present with the largest female (3.64 m DW) 18% larger than the largest male (3.03 m DW). Sexual maturity in females, based on evidence of pregnancy and mating scars, was conservatively determined to be 3.37 m DW. The DW at which 50% of the males were likely to be mature (based on clasper length) was between 2.7 and 2.8 m. The absence of individuals < 2.5 m DW suggests that age class segregation occurs in this population. Paired-laser photogrammetry proved to be a simple, non-invasive, accurate, and precise method for sizing free-ranging manta rays. Repeated measurements on known individuals over time could provide population growth parameters needed for adequate management of this poorly understood species.

Two unusual interactions between a bottlenose dolphin (Tursiops truncatus) and humpback whale (Megaptera novaeangliae) in Hawaiian waters.

Deakos M.H., Branstetter, B.K., Mazzuca, L., Fertl, D., Mobley J.R.Jr. (2010) Aquatic Mammals 36(2):121-128

Abstract
When two species share a common habitat, interspecific interactions can take many forms. Understanding the dynamics of these interactions can provide insight into the behavior and ecology of those species involved. Two separate, unusual interactions are described in which a humpback whale (Megaptera novaeangliae) lifted a bottlenose dolphin (Tursiops truncatus) completely out of the water. Both incidents occurred in Hawaiian waters. Based on reports of object play by humpback whales, and the apparent initiation and cooperation of each dolphin being lifted, object (i.e., the dolphin) play by the whale and social play by the dolphin seem to be the most plausible explanations for the interaction. Aggressive and epimeletic behavior by the humpback were also considered.

Male humpback whales in the Hawaiian breeding grounds preferentially associate with larger females.

Pack A, Herman L, Spitz S, Hakala S, Deakos M, Herman E (2009). Animal Behaviour 77(3):653-662

Abstract
The competitive group appears to be a major component of the mating system of the humpback whale, Megaptera novaeangliae, bringing together a single female (nuclear animal or NA) and multiple males (escorts) that compete for physical proximity to her. We examined the relation of body size of the NA to the number of attending escorts and, separately, we determined the relation of a female's body size to the size of her calf. Using underwater videogrammetry in Maui waters during 1997–2002, we measured the body length of the NA in each of 42 competitive groups. We also measured the lengths of the mother and her calf in each of 92 mother–calf groups. The number of initial escorts in a competitive group was positively correlated with NA body length. Longer mothers were associated with longer calves, even after accounting for seasonal differences in calf length. We conclude that male humpback whales prefer to associate with larger females and that larger females produce larger calves. Theoretically, larger calves have a greater chance of survival than do smaller calves. The choice of a larger female may therefore increase the reproductive success of an escort that succeeds in mating.

Using Paired-Laser Photogrammetry for Measuring Manta Ray (Manta birostris) Sizes. Are Maui’s Mantas Horizontally Challenged?

Deakos, Mark (2008). Abstract, 88th annual meeting of the American Society of Ichthyologists and Herpetologists, Montreal, Canada

Abstract
Paired-laser photogrammetry was used to measure the disc width (DW) of 78 manta rays (Manta birostris) from a nearshore Maui population. The mean ratio of DW to disc length (DL) for 43 of these individuals was 2.30 (N=43, SD=0.10). The mean ratio for mature males (determined by the claspers extending beyond the pelvic fins) was not significantly different than that for immature males (t (14)=0.59, p=0.56) indicating that the DW to DL proportion remains constant throughout development. DL measurements were more reliable and more easily obtained than DW measurements using paired-laser photogrammetry. Given this, DL measurements were used and converted to the more conventional DW measurement equivalent using the ratio of 2.30. Female DW ranged from 2.42 m to 3.70 m (mean=3.22 m, N=40). The maximum female DW in this population is 25% smaller than the maximum reported for a female in Indonesia (White et al., 2006), and as much as 59% smaller than that reported in other parts of the world (Last & Stevens, 1994). Male DW ranged from 1.98 m to 3.18 m (mean=2.80 m, N=33). The maximum male DW in this population is 22% smaller than the maximum DW reported for a male in Indonesia (White et al., 2006). Males were sexually mature at a DW greater than 2.79 m, (N=20), 27% smaller than what has been reported for males in Indonesia. These results support paired-laser photogrammetry as a non-invasive and precise method for sizing manta rays in the field and suggest that manta rays in Maui mature and grow to a much smaller body size than what is observed in Indonesia and other populations worldwide. The absence of killer whales in Hawaii, a reported predator of manta rays, may alleviate natural selection pressures for large body size as a beneficial trait in predatory defense.

Demographics of an Island-Associated Manta Ray (Manta birostris) Population in Maui, Hawaii, and Implications for Management

Deakos, Mark, Jason Baker, Allan Ligon, Jonathan Whitney, Tim Clark (2008). Abstract, 88th annual meeting of the American Society of Ichthyologists and Herpetologists, Montreal, Canada.

Abstract
During 2005 - 2007, 187 individual manta rays were photo-identified from a single
cleaning station site in Maui, Hawaii. A discovery curve showed no asymptotic trend,indicating the number of individuals using the site is considerably larger than the total identified. Of these individuals, 58% were observed on more than one occasion within and across years, suggesting philopatry to this area. Males accounted for 47% of the individuals in the population, of which 69% were considered sexually mature based on the claspers extending beyond the pelvic fins. The average encounter rate per dive was 5.50 manta rays per hour. They were habitually absent at first light, with encounter rates increasing throughout the day. No matches were found when compared against 133 individuals photo-identified from a well-studied population off the Big Island (www.mantapacific.org), a distance of only 60 miles. Evidence of shark predation was seen in 12% of the population, and 6% had a missing or non-functional cephalic fin, likely caused by entanglement in monofilament fishing line. During an intensive survey period from September to December 2007, a mean of 140 individuals (95% CI = 119- 175) was estimated to be using the area at this time. Estimated annual apparent survival
(survival minus emigration) was 0.77 (95% CI = 0.65 – 0.86). These findings are
consistent with a population of manta rays moving into and out of the cleaning station vicinity, with a varying portion of the total population temporarily resident at the study site at any given time. These findings add further support to the existence of demographically independent, island-associated populations in Hawaii. The lack of protection for these populations makes them vulnerable to impacts from target and nontarget fisheries, and from exploitation of manta ray aggregation sites by commercial scuba diving operations. Management on an island-area basis is recommended.

Population structure of island-associated dolphins: evidence from photo-identification of common bottlenose dolphins (Tursiops truncatus) in the main Hawaiian Islands.

Baird, R.W., A.M. Gorgone, D.J. McSweeney, A.D. Ligon, M.H. Deakos, D.L. Webster, G.S. Schorr, K.K. Martien, D.R. Salden, S.D. Mahaffy. (2008). Marine Mammal Science, in Press.

Abstract
Management agencies often use geopolitical boundaries as proxies for biological boundaries. In Hawaiian waters a single stock is recognized of common bottlenose dolphins, Tursiops truncatus, a species that is found both in open water and near-shore among the main Hawaiian Islands. To assess population structure, we photo-identified 336 distinctive individuals from the main Hawaiian Islands, from 2000-2006. Their generally shallow-water distribution, and numerous within-year and between-year re-sightings within island-areas suggest that individuals are resident to the islands, rather than part of an offshore population moving through the area. Comparisons of identifications obtained from Kaua‘i/Ni‘ihau, O‘ahu, the “4-island area”, and the island of Hawai‘i showed no evidence of movements among these island groups, although movements from Kaua‘i to Ni‘ihau and among the “4-islands” were documented. A Bayesian analysis examining the probability of missing movements among island groups, given our sample sizes for different areas, indicates that inter-island movement rates are less than 1% per year with 95% probability. Our results suggest the existence of multiple demographically- independent populations of island-associated common bottlenose dolphins around the main Hawaiian islands.

False killer whales (Pseudorca crassidens) around the main Hawaiian Islands: long-term site fidelity, inter-island movements, and association patterns.

Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden, M.H. Deakos, A.D. Ligon, G.S. Schorr, J. Barlow and S.D. Mahaffy. (2008). Marine Mammal Science, 24(3), 591-612

Abstract
Despite their world-wide distribution throughout the tropics and subtropics, false killer whales (Pseudorca crassidens) are one of the lesser-known large odontocetes. Genetic evidence indicates a demographically isolated population around the main Hawaiian Islands. We examine site fidelity, movements and association patterns in this population using data from directed surveys and opportunistic photographs from 1986 to 2007. This species was only infrequently encountered, and while found in depths from 38 to 4,331 m, sighting rates were greatest in depths >3,000 m. We photo-identified 152 distinctive individuals. Resighting rates were high, with an average of 76.8% of distinctive individuals within groups documented on more than one occasion. Most (86.6%) were linked by association into a single social network; only one large group (16 distinctive individuals), documented the farthest offshore (42–70 km), did not link by association to that large network, and may be part of an offshore population. Individual movements of up to 283 km were documented, with a large proportion of individuals moving among islands. Individuals were resighted up to 20.1 yr after first being documented, showing long-term fidelity to the islands. Repeated associations among individuals were documented for up to 15 yr, and association analyses indicate preferred associations and strong bonds among individuals.

The acoustic field of singing humpback whales in the vertical plane.

Au, W. W. L., Pack, A. A., Lammers, M. O., Herman, L. M., Andrews, K., & M. H. DeakosThe Journal of the Acoustical Society of America, April 2003, Volume 113, Issue 4, p. 2277

Abstract
A vertical array of five hydrophones was used to measure the acoustic field of singing humpback whales. Once a singer was located, two swimmers with snorkel gear were deployed to determine the orientation of the whale and to position the boat so that the array could be deployed in front of the whale at a minimum standoff distance of 10 m. The spacing of the hydrophones was 7 m with the deepest hydrophone deployed at depth of 35 m. An 8-channel TASCAM recorder having a bandwidth of 24 kHz was used to record the hydrophone signals. The location of the singer was determined by computing the time of arrival differences between the hydrophone signals. The maximum source level varied between individual units in a song, with values between 180 and 190 dB. The acoustic field determined by considering the relative intensity of higher frequency harmonics in the signals indicate that the sounds are projected in the horizontal direction with the singer's head canted downward 45 to 60°. High-frequency harmonics extended beyond 24 kHz, suggesting that humpback whales may have an upper frequency limit of hearing as high as 24 kHz.

Humpback whale (Megaptera novaeangliae) communication: The context and potential functions of pec-slapping behavior on the Hawai'ian wintering grounds.

Deakos, M. H.
Unpublished Masters Thesis, University of Hawaii, Manoa, 2002

Abstract
Humpback whales display a variety of percussive behaviors that may function as communication between conspecifics. Pectoral-fin slapping behavior is commonly observed in a variety of marine mammals including seals, dolphins, and humpback whales. Data from 5-years of behavioral observations of humpback whales on the Hawaiian wintering grounds were compiled and analyzed. Overall findings suggest pecslapping behavior is dependent on the performer’s age class, sex, and social role. Adult females appear to pec-slap in competition groups in efforts to encourage competition from surrounding males, indicating her readiness to mate. Adult males pec-slap while disaffiliating from other males, possibly in attempts to maintain a non-agonistic male association. Subadult pec slapping is likely a form of “play”, an important characteristic in the development, coordination, and learning in young mammals. These discoveries can serve as tools to enhance the interpretation of humpback whale social behavior, and provide a model for understanding other percussive behaviors.

The relation of body size of male humpback whales to their social roles on the Hawaiian winter grounds.

Scott S. Spitz, Louis M. Herman, Adam A. Pack, and Mark H. Deakos
Canadian Journal of Zoology, 2002. Volume 80, Issue 11, pp. 1938-1947

Abstract
We examined the relation of body length of male humpback whales (Megaptera novaeangliae) to the social roles they adopted on the Hawaiian winter grounds: principal escort in a competitive group, secondary escort, lone escort to a mother–calf pair, male partner in a dyad, and singer. Using underwater videogrammetry, we measured body lengths of 17 principal escorts, 68 secondary escorts, 40 single escorts, 17 male partners, and 8 singers. Results revealed that (i) principal escorts were, on average, significantly larger than males in each of the remaining social roles except singer, (ii) singers were significantly larger than male partners, (iii) there were no significant size differences among secondary escorts, single escorts, or male partners. Further, principal escorts tended to be the largest or second-largest male within their individual competitive group. All principal escorts were of sizes that indicated a 0.81 probability or better of sexual maturity, based on whaling data. In comparison, more than half of the male partners, almost one-third of the secondary escorts, and one-fifth of the single escorts were of sizes that indicated a 0.5 probability or less of sexual maturity. Seven of the eight singers had a 0.9 probability or better of sexual maturity and the eighth singer a 0.5 probability. However, the data for singers are too few to allow firm conclusions to be reached about the relation of body size to singing. Overall, our findings suggest that body size confers an advantage in physical competition between male humpback whales, and that a large proportion of males adopting the role of secondary escort, single escort, and partner are likely to be sexually immature. Additionally, the competitive group appears to be a major reproductive unit in terms of bringing together a receptive female and potential mates.

Penis extrusions by humpback whales (Megaptera novaeangliae).

Pack, A. A., L. M. Herman, A. S. Craig, S. S. Spitz and M. H. Deakos
Aquatic Mammals, 2002, Volume 28, Issue 2, pp. 131-146

Abstract
The annual winter assembly of humpback whales (Megaptera novaeangliae) in tropical waters has been linked to reproductive activities, including birthing, calf-rearing, and mating. However, the sexual behaviour of this species remains largely undescribed and mating has never been witnessed. We examined 121 h of underwater videotaped footage of humpback whales obtained over five winter seasons in Hawaiian waters for evidence of penis extrusions by whales engaged in various activities in a range of social groups. In 630 different pods containing videotaped males, we noted 13 penis extrusion incidents. Penis extrusions were performed by lone singers (2 incidents), by the single escort to a mother/calf pair (6 incidents), and by principal and secondary escorts in competitive pods containing a female either with a calf (2 incidents) or without (3 incidents). All penis extrusions were brief (mean=44.0) s). Body length measurements (mean=11.53 m, SD=0.46 m, range=10.64 m to 12.05 m) were obtained using underwater videogrammetry on seven penis extruders, and suggested that the majority were sexually mature. Each penis extrusion in a competitive pod coincided with the penis extruder chasing another whale, and in four of five cases appeared to be directed toward another male. In the remaining case, the extruder appeared to attempt mating with a mother. Our findings suggest that penis extrusions in humpback whale competitive pods are often a concomitant of dominance contests between males.

False killer whales around the main Hawaiian islands: an assessment of inter-island movements and population size using individual photo-identification.

Baird, R.W., A.M. Gorgone, D. L. Webster, D.J. McSweeney, J.W. Durban, A.D. Ligon, D.R. Salden, and M.H. Deakos.
Report prepared under Order No. JJ133F04SE0120 from the Pacific Islands Fisheries Science Center, National Marine Fisheries Service, 2570 Dole Street, Honolulu, HI 96822, April 5, 2005

Abstract
The current best estimate of population size for false killer whales within Hawaiian waters is only 268 individuals (Barlow 2003), though the estimate is not very precise (CV = 1.08). False killer whales are considered a “strategic” stock by the National Marine Fisheries Service, as “takes” in the Hawai‘i-based swordfish and tuna long-line fishery exceed the “Potential Biological Removal” (PBR) level. We studied false killer whales as part of small-boat based surveys for odontocetes around the main Hawaiian islands from 2000 through 2004, and in this report we assess inter-island movements, examine “mark” change over time on individual animals, estimate the proportion of marked individuals within the population, and provide a mark-recapture population estimate. Dedicated surveys for odontocetes were undertaken around all the main Hawaiian islands, and all groups of false killer whales encountered were approached and attempts made to photographically identify all individuals present. False killer whales were encountered on 14 occasions in directed surveys (2.9% of all odontocete sightings), in eight of the 10 months of the year surveyed, and in three of the four island-areas surveyed. Encounters were in a wide range of water depths (37 to 3,950 m). Photographs from seven opportunistic encounters were also available. Seventy-seven percent of individuals photographed were considered to have markings that could be recognized in the long-term (between-years). Seventy-six individuals with such long-term markings were documented, 47 of which were seen on two or more occasions. Ten individuals were documented with mark changes, though the rate of mark change was low (approximately one change every six years). Re-sighting analysis suggest that there are considerable inter-island movements of individuals (for example, 19 of 21 individuals identified off O‘ahu have been recorded off the island of Hawai‘i or around the “4-islands”). A multi-site mark-recapture analysis, taking into the proportion of marked individuals in the population, resulted in an estimate of 123 individuals in the population (CV = 0.72). This estimate applies to a population of false killer whales that used the study area; however the geographic range of that population is not known. Also, we assumed population closure and homogenous capture probabilities among individuals. The degree to which these assumptions may have been violated and the resulting estimate biased remain unclear.

Determining source levels and sound fields for singing humpback whales (Megaptera novaeangliae) on the Hawai'ian wintering grounds.

Adam A. Pack, John R. Potter, Louis M. Herman, Mark H. Deakos, Matthias Hoffmann-Kuhnt
ECOUS Symposium, 12-16 May 2003, San Antonio, Texas

Abstract
Male humpback whales (Megaptera novaeangliae) on their wintering grounds produce complex vocalizations termed “song.” The stereotypical stationary posture adopted by singers suggests they are attempting to optimize transmission range. In March 2002, we measured the sound fields of singers using divers equipped with rebreather scuba. A customdesigned ‘Aquahead’ system reliably located ECOUS Symposium 12-16 May 2003 San Antonio, TX 10 singers to within 30 m. Fourteen singers were located from as far away as 8.2 km and in times of 11-48 min. The rebreathers enabled divers to descend to the singer with minimal expulsion of bubbles and noise. Divers moved in arcs around the singer to sample song at various orientations using digital video cameras while simultaneously measuring depth and range to the singer’s head using handheld ultrasonic range meters. At the end of a song a snorkeler used our videogrammetric technique to measure singer body length. Initial signal processing of five singers indicates source powers of up to 190 dB re 1 microPa @ 1 m with a directionality oriented in front of the singer’s head, lateral power levels being up to 18 dB below those in front at some frequencies. Higher frequencies were observed to have a higher directionality than lower frequencies.

Why do humpback whales slap their pectoral fins in competitive groups?

Deakos, M. H., Pack, A. A., Herman, L. M., and Spitz, S. S.
Poster presented at the 14th Biennial conference on the biology of marine mammals, Vancouver, Canada, November 28 – December 5, 2001

Abstract
Humpback whales on their wintering grounds are often observed in “competitive groups” composed of multiple males competing physically for proximity (principal escort position, PE) to a lone female (nuclear animal, NA) or to one accompanied by her calf (mother). Although several behaviors in competitive groups are clearly related to male-male aggression, others are less well understood. Slapping a pectoral fin against the water surface (pec slap) is sometimes observed in competitive as well as non-competitive groups. We investigated the social roles and contexts of pec slapping in competitive groups over 5 winter seasons (1997 – 2001) in Hawaiian waters. Overall, pec slapping was recorded in 256 (31%) of 831 competitive groups (the mature female (either NA or mother) pec slapped in 42% of the 256 groups, the PE in 5%, and secondary escorts in 17%). Of 636 NA competitive groups, the NA pec slapped in 94 (15%), compared with only 14 (7%) mothers pec slapping in 196 competitive groups (x2 = 7.1, p < .01). PEs pec slapped in only 3 (0.5%) of NA competitive groups compared with 9 (5%) in mother/calf competitive groups (x2 = 21.3, p < .001). Because mature female humpbacks without calf are more likely to conceive, NAs should theoretically have a higher reproductive potential than mothers (Craig, 2001). Males might therefore be expected to compete more vigorously in competitive groups without calf. The lower percentage of pec slapping by PEs in groups without calf suggests that pec slapping is not a principal competitive behavior employed by males. If pec slapping by females in competitive groups were related to female receptivity, it should be greatest in pods without calf. If it were related to deterring males, it should be greatest in competitive pods in which females are less receptive. Our findings are consistent with the first hypothesis.

Survival and recovery of a humpback whale calf with a grievous propeller wound.

Deakos, M. H., Pack, A. A., Herman, L M., Spitz, S. S., and Craig, A. S.
Poster presented at the 13th Biennial conference on the biology of marine mammals, Wailea, Maui, USA, November 28 – December 3, 1999

Abstract
Recovery from serious injury has been well documented for dolphins. However, little data exist on the recuperative capabilities of baleen whales. Calves, because of their relatively small size, may be particularly vulnerable. In 1999, a humpback whale calf (C) with a deep gash in its back was observed on four occasions over 38 days in waters off Maui. The wound extended rostrally from the dorsal fin 31-cm, was 17-cm deep, penetrating through blubber, and stretched 56-cm down the left side. No bleeding was observed, and the presence of granulated tissue suggested that healing had begun. Three vertical lacerations indicated injury from a boat propeller. Changes in C's behavior and its mother's (M) dive duration provided evidence of C's recovery. Initially, M attended C closely, repeatedly supporting C after it surfaced and rolled onto its side. Dive times for both M and C were only 30 s. Twenty-three days later, C surfaced with no apparent difficulty. However, it was still joined by M at each surfacing. Mean dive times for M and C were 3.68 and 2.80 min, respectively. Three days later C appeared energetic and behaved like healthy humpback calves. C milled at the surface before diving to M and breached repeatedly within a 5-min period following affiliations by multiple escorts. It traveled within this competitive group 8.53 km in 2 hr 15 min with top speeds reaching 4.59 km/hr. Eleven days later, C was again observed breaching as it traveled. Mean dive times increased to 6.36 min for M but remained relatively unchanged for C, possibly indicating C's decreasing requirement for support at the surface. Although boat strikes are an increasing problem for cetaceans, our findings suggest that like dolphins, humpback whale calves are able to recover from some major physical traumas.