Allometric Relationships and Sexual Dimorphism in Captive Killer Whales (Orcinus orca)

Clark, Steven T.; Odell, Daniel K.

doi:10.2307/1383247

Cited by 32 publications

(29 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sex and regional differences were found in the distance between the tip of the lower jaw to both the genital slit and the blowhole and in the width of the tail fluke. The genital slit opening is known to be more anterior in male cetaceans (Clark & Odell, ). The larger rostrum to blowhole measurement found in females is concordant with the findings of the analyses of cranial measurements in that females clearly have longer rostra than males.…”

Section: Resultssupporting

confidence: 90%

“…The most extreme size differences occur in sperm whales, where females reach around 11 m in length (15 tonnes) but males regularly grow to 16 m in length and 45 tonnes (Ralls & Mesnick, ). Differences in the shape and size of appendages, head and teeth are seen in many species such as narwhals ( Monodon monoceros ), killer whales ( Orcinus orca ) and belugas ( Delphinapterus leucas ; Clark & Odell, ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Large‐scale multivariate analysis reveals sexual dimorphism and geographic differences in theGray's beaked whale

et al. 2014

View full text Add to dashboard Cite

Gray's beaked whales (Mesoplodon grayi) are medium‐sized odontocete (toothed) cetaceans that are members of the family Ziphiidae. These animals inhabit deep oceanic waters and are rarely seen at sea. Most information is derived from stranded animals and there has been no systematic study of their morphology. We present a multivariate analysis of the morphology of Gray's beaked whales using 80 cranial measurements from 22 individuals and 13 external measurements from 50 individuals. Sparse principal component and linear discriminant function analyses were used to classify samples into sexes. Males and females have markedly different cranial morphology. In particular, females have longer skulls with longer more slender rostra (beaks) in comparison to males. Two variables, depth of the rostrum at mid‐length and tip of rostrum to the right temporal fossa, can classify sex with 100% accuracy. The external body measurements used in this study are more prone to error as they were recorded by a number of observers on carcasses in differing states of decomposition and this is reflected in the level of variance in most measurements. However, analyses of these measurements showed a significant difference between sexes in the distance between (1) the tip of the rostrum to the genital slit, (2) the tip of the rostrum to the blowhole, as found in the cranial analyses and (3) tail fluke width where males have absolutely wider tail flukes than females. Differences in these same measurements were also found between animals stranded on the east and west coasts suggesting a degree of population separation across New Zealand. Finally, we present two linear models that enable the assignment of sex from either skull or external measurements. These models will be useful for future studies as well as the management of these whales and can be applied to archived data where genetic sex assignment is not possible.

show abstract

Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Large‐scale multivariate analysis reveals sexual dimorphism and geographic differences in theGray's beaked whale

et al. 2014

View full text Add to dashboard Cite

show abstract

“…It is common for cetaceans to have allometric growth, e.g ., common bottlenose dolphin, Tursiops truncatus (Félix et al . ) and killer whale (Clark and Odell ), or a combination of feature‐specific allometric and isometric growth, e.g ., long‐finned pilot whale, Globicephala melas (Sergeant ); Dall's porpoise, Phocoenoides dalli (Amano and Miyazaki ); dusky dolphin, Lagenorhynchus obscurus (Van Waerebeek ); and vaquita, Phocoena sinus (Torre et al . ).…”

Section: Discussionmentioning

confidence: 99%

How to tell them apart? Discriminating tropical blackfish species using fin and body measurements from photographs taken at sea

Yahn

Baird

Mahaffy

et al. 2019

Marine Mammal Science

View full text Add to dashboard Cite

The misidentification of species and populations is a hindrance to effective cetacean management. We devised a method of species identification using 10 fin and body measurements obtainable from at‐sea photographs, and demonstrated its ability to distinguish four species of Hawaiian “blackfish”: pygmy killer, melon‐headed, short‐finned pilot, and false killer whales. Measurements from photos of 382 known individuals were converted into 14 ratios and reduced using nonmetric multidimensional scaling and principal component analysis. The first three components of the PCA explained 81% of variance among species. Ratios indicated by PCA and NMDS were tested using analysis of variance, and results identified three fin ratios that had distinct means across all four species: height/base, depth (from anterior insertion) at trailing edge apex/depth at topmost point, and width (from leading edge) at posterior point/base. Dual analysis of adults and all age classes showed near‐identical sources of variance, 90% similarity in interspecies ratio relationships, and overlapping ratio means and ranges. Results suggest similar ontogenetic growth across these four species, and confirm the efficacy of this discrimination technique for all age classes. This study established a reliable means of distinguishing these cetacean species, which will improve the efficacy of management in areas with sympatric distributions.

show abstract

“…Killer whales can turn at a maximum rate of 233º/s at 6 m/s within a radius of 0.11 body lengths by using the flippers in combination with peduncle, and flukes (Fish ). Mature male killer whales have disproportionately large flippers that are 1.7 times longer than females (Clark and Odell , Ford ). This size differential can be associated with sexual differences in hunting and maneuvering performance by transient killer whales, as the females are mainly responsible for corralling prey (Pitman et al .…”

Section: Discussionmentioning

confidence: 99%

Hydrodynamic performance of the flippers of large‐bodied cetaceans in relation to locomotor ecology

Weber

Howle

Murray

et al. 2013

Marine Mammal Science

View full text Add to dashboard Cite

Cetaceans evolved flippers that are unique in both size and shape probably due to selection pressures associated with foraging and body size. Flippers function as control surfaces for maneuverability and stability. Flippers of cetaceans and engineered hydrofoils are similar with streamlined cross‐sections and wing‐like planforms, which affect lift, drag and hydrodynamic efficiency. Scale models of the flippers from large‐bodied (body length > 6 m) cetaceans (fin whale, killer whale, sperm whale) were constructed from computed tomography (CT) scans of flippers. Flipper planforms were highly tapered for the fin whale, a rounded, paddle‐like design for the killer whale, and a square geometry for the sperm whale. Hydrodynamic properties of the models at varying angles of attack (−40º to 40o) were determined in a water tunnel with a multi‐axis load cell. The flippers were found to have hydrodynamic characteristics similar to engineered wings. Differences in flipper morphology of large‐bodied cetaceans and their hydrodynamic performance are associated with the requirements of aquatic locomotion involved with ecology of the whales. The flippers of the killer whale provided the greatest maneuverability, whereas the flippers of the fin whale had low drag for lunging and the flippers of the sperm whale provided lift for diving.

show abstract

Allometric Relationships and Sexual Dimorphism in Captive Killer Whales (Orcinus orca)

Cited by 32 publications

References 10 publications

Large‐scale multivariate analysis reveals sexual dimorphism and geographic differences in theGray's beaked whale

Large‐scale multivariate analysis reveals sexual dimorphism and geographic differences in theGray's beaked whale

How to tell them apart? Discriminating tropical blackfish species using fin and body measurements from photographs taken at sea

Hydrodynamic performance of the flippers of large‐bodied cetaceans in relation to locomotor ecology

Contact Info

Product

Resources

About