Dorsal Skin Color Patterns Among Southern Right Whales (Eubalaena Australis): Genetic Basis and Evolutionary Signi®Cance

Dorsal Skin Color Patterns Among Southern Right Whales (Eubalaena australis): Genetic Basis and Evolutionary Signi®cance

C. M. Schaeff, P. B. Best, V. J. Rowntree, R. Payne, C. Jarvis, and V. A. Portway

Distribution and inheritance of dorsal skin color markings among two populations of southern right whales (Eubalaena australis) suggest that two genes in¯uence dorsal skin color. The grey-morph and partial-grey-morph phenotypes (previously known as partial albino and grey-blaze, respectively) appear to be controlled by an X-linked gene, whereas the white blaze appears controlled by an autosomal gene (recessive phenotype). Calving intervals, calf size, and length of sighting history data suggest that partial-grey-morph, white-blaze, and black cows experience similar levels of reproductive success. Grey-morph cows (XgXg) are rare or absent in the two populations, but this was not unexpected given observed population frequencies of grey-morph males (XgY) and partial-grey-morph females (XGXg). The proportion of partial-grey-morph calves produced by black cows (XGXG) suggests that the reproductive success of grey-morph males was equal to that of black males, however, larger sample sizes are required to determine whether grey-morph males tend to have shorter sighting histories. The reproductive success of white- blaze males appeared similar to that of black males among whales off Argentina. There were signi®cantly fewer white-blaze calves than expected off South Africa, From the Biology Department, American University, 4400 Massachusetts Avenue NW, Washington, D.C. which could be due to white-blaze males experiencing reduced reproductive suc- 20016 (Schaeff, Jarvis, and Portway), Mammal Re- cess or to sighting biases that result in white-marked calves being misidenti®ed search Institute, University of Pretoria, Pretoria, South Africa (Best), and Whale Conservation Institute, 191 as black calves. The relative frequencies of both types of dorsal color markings Weston Rd., Lincoln, Massachusetts (Rowntree and varied between the South African and Argentinian right whale populations, sug- Payne). The collection of the South African samples gesting limited nuclear gene ¯ow between these populations; analyses using other was made possible through the financial support of the Foundation for Research Development and Earthwatch nuclear markers are under way to con®rm the extent of gene ¯ow. and the participation of volunteers S. Edwards, D. Pe- trucco, M. Whiston, C. Maul, N. Schlocker, L. Boast, D. Five dorsal skin color patterns have been splotch mutations in mice, which result in Hauenstein, M. Ketting, J. Marnoch, B. Honchorek, P. Pond, O. Weisshuber, S. Ruegg, E. Welsh, S. Margison, documented among southern right whales reduced survival (Goulding et al. 1993; Ho- S. Santra, K. Babiak, S. Jacobs, R. Mobbs, H. Achen- (Eubalaena australis): black, white-blaze, soda et al. 1994), and Chediak–Higashi bach, E. Lock, S. MacDonald, E. Dickens, D. Schmitz, C. Whitfield, M. Berkstresser, F. Frischknecht, B. Schnaar, grey-blaze, grey-and-white-blaze, and par- syndrome (homologous to beige in mice and D. Shull is much appreciated. Invaluable field as- tially albinistic (Best 1990; Payne et al. and Aleutian disease in mink; Jackson sistance was also provided by D. Reeb, M. Sanson, D. 1983) (Table 1; Figure 1). Partially albinis- 1997), which is associated with an in- Kemp, D. Calder, R. Cloete-Hughes, K. Findlay, K. Cal- der, L. Staverees, M. Best, and C. du Plooy. We are tic right whales are white as calves but creased susceptibility to infection. It is un- grateful to all the graduate students, researchers, pi- darken and become grey or brownish-grey clear what, if any, effect partial albinism or lots of the Aeroclub of Trelew, friends and volunteers as they age (Best 1990; Payne et al. 1983; the other right whale pigment patterns who assisted in the collection and analysis of aerial survey data of the right whales off Argentina. In Argen- Figure 2). These calves lack the pink eyes have on an individual’s viability. tina, we also thank the Organismo Provincial de Tur- associated with true albinism and have a A number of southern right whale pop- ismo for permits to conduct the research, the Wildlife Conservation Society for use of the research station, scattering of black pigmentation which is ulations have been studied intensely over and Estancia La Adela for use of their landing strip. We usually distributed in a narrow transverse the past two decades, but investigations are especially grateful to Aerolineas Argentinas, the band posterior to the blow holes that ex- of right whale color patterns have been Fundacion A. Fortabat, S. Haney, Metcalf and Eddy, Inc., Minolta Inc., the National Geographic Society, People’s tends partway down the side in the shoul- hampered by an inability to determine Trust for Endangered Species, the Wildlife Conserva- der region. The marks on grey-blaze ani- many animals’ sex. Methods do exist for tion Society, and the World Wildlife Fund for support mals are also white in calves but darken sexing right whales in the field (e.g., adult- of research in Argentina. Financial support for the genetic analyses was provided by the American Univer- as the animals age. calf associations or observations of sex- sity and the Pittsburgh Zoo. Samples were collected A number of white pigmentation pat- specific morphology such as a penis or under a permit issued to PBB by the South African De- partment of Environment Affairs and imported in ac- terns are associated with pathological genital slits), however, because of the op- cordance with U.S. regulations (NMFS #825432, NOAA conditions including dominant white spot- portunistic nature of the methodology, #1019). We thank J. Seger for helpful discussions and ting (homologous to c-kit in pigs) and many animals (especially males) remain comments on the manuscript. Address correspon- dence to C. M. Schaeff at the address above or e-mail: steele (homologous to kit ligand in mice; unsexed even after years of behavioral [email protected]. see Silvers 1979 for review), which result work (Schaeff et al. 1993). Fortunately, re- ᭧ 1999 The American Genetic Association 90:464–471 in lower fertility and anemia, piebald and cent advances in molecular biology have

464 Table 1. Southern right whale dorsal color markings

Pattern Descriptiona

Black Dorsal skin is black. White-blaze Animal has an unpigmented area with edges that are distinct and straighter than in partial-grey- morph; marks remain white through the animal’s life. Grey-morpha,b Animals are mostly white as calves but their skin darkens with age and adults appear grey or brownish-grey. Grey-morphs tend to have scattered black spots that are often in a band behind and spread laterally over the shoulder. Partial-grey- Animal has a mark that is white in morpha calves but darkens with age; similar to grey-morph adults but with much less white. Markings are more complex and have a rounded edge compared to white blazes. Marks appear to be formed by many overlapping circles of white and sometimes there are circular inclusions of black within a par- Figure 1. Female right whale with both grey and white blazes with her grey-morph calf. (Photographer: K. Payne) tial-gray region. Partial-grey- Partial-grey-morph animals with a morph with a white blaze; marks are usually as- vide a more accurate label for the animals imals encountered during a survey were white-blaze sociated. previously known as partially albinistic. photographed. a Phenotypes defined previously (Best 1990; Payne et al. We refer to animals that are born predom- Calf body length measurements were 1983) but with different nomenclature: grey-morph pre- inantly white but then darken to grey as taken photogrammetrically from a heli- viously referred to as partial albino, partial-grey-morph as grey-blaze. grey-morph animals (previously partially copter off South Africa in 1988 and 1989 b Grey-morph animals with white blazes also exist but albinistic), animals that have a white mark using a radar altimeter to establish range are difficult to distinguish during aerial surveys from that darkens to grey as partial-grey- (Best and Ru¨ther 1992). grey-morph animals that do not have a white blaze; for this study, category II includes all grey-morph animals. morphs (previously grey-blazed), and animals with a white mark that remains Sexing white throughout their life as white-blaze Right whales were sexed (1) by viewing resulted in the development of several (no change in nomenclature). The marks their genital slits (females and males), (2) methods for determining sex genetically on white-blaze and partial-grey-morph an- behaviorally (adults seen in associations [e.g., Southern hybridization with a Y-chro- imals are generally very easy to distin- with calves were assumed to be females), mosome-specific probe, pDP1007 (Page guish (Table 1). or (3) genetically (females and males; et al. 1987); polymerase chain reaction Schaeff and Best 1998). (PCR) amplification of sex-specific prod- Materials and Methods Small skin samples were collected from ucts (Be´rube´ and Palsbøll 1996; Bradbury free-ranging right whales using a Paxams et al. 1990; Palsbøll et al. 1992)]. Sighting Data dart gun loaded with lightweight polycar- For this study, we collected skin biopsy Right whales can be individually identified bonate darts. Darts were fitted with stain- samples from free-swimming right whales by their callosity patterns, scars, and skin less steel tips designed to receive and se- off South Africa and determined their sex color markings (Best 1990; Kraus et al. cure small (0.5–1.0 g) skin samples and genetically using a PCR-based, three-prim- 1986; Payne et al. 1983). Near-vertical ae- then float on the surface of the sea (Best er system for the ZFY/ZFX sex-chromo- rial photographs were taken of right et al., in preparation). Skin samples were some-specific region (Be´rube´ and Palsbøll whales off the South African coast during stored in a preservative solution of super- 1996). We analyzed the frequency of pig- helicopter surveys of the coastline each saturated NaCl and 20% dimethylsulfoxide ment patterns in right whale populations year from 1979 to 1996 [see Best (1990) for (DMSO) at 4ЊC. off South Africa and Argentina in conjunc- details]. Flights were directed primarily to- DNA was extracted from the skin sam- tion with cow-calf transmission patterns ward mother-calf pairs; other animals ples using lysis buffer and proteinase K, to identify possible genetic mechanisms were photographed only when in groups followed by phenol/chloroform extrac- for the color types. The evolutionary sig- with mother-calf pairs. Between 1995 and tions as described in Schaeff et al. (1993). nificance of the color patterns was inves- 1996, animals were photographed from The ZFY/ZFX sex-specific regions were tigated by examining the reproductive boats prior to biopsy collection; all cate- then amplified by PCR using primers success of males and females with differ- gories of animals were photographed dur- ZFYX0582F, ZFY00767R, and ZFX0785R ent color markings. ing this period. (Berube and Palsbøll 1996). Approximate- We have changed the nomenclature for The population of right whales off Pen- ly 50 ng of genomic DNA was used as tem- right whale dorsal skin color phenotypes insula Valde´s, Argentina, has been photo- plate in each 20 ␮l reaction (67 mM Tris-

to avoid confusion between white blazes graphically surveyed from ﬁxed-wing air- HCl, pH 8.8, 1.5 mM MgCl2, 16 mM

that remain white throughout an animal’s craft each year from 1971 through 1997 (NH4)2SO4, 60 mM tetramethylammonium life and the marks that darken, and to pro- [see Payne et al. (1983) for details]. All an- chloride, 200 mM dNTPs, 0.5 ␮M each

Schaeff et al • Right Whale Dorsal Markings 465 those without, and hence used only five categories for this study (Table 1). Using sighting data, the relative frequency of each color marking was determined for three groups of animals: cows, calves (animals in their first year of life), and noncalves (all animals sighted after their first year, including cows). Adult male frequencies were estimated from the noncalves data by assuming (1) a 1:1 sex ratio among noncalves and (2) that the color pattern proportions observed among known cows are representative of all noncalf females. Mode of inheritance was investigated by analyzing the distribution of marking patterns among animals of known sex and by analyzing skin color inheritance patterns among cow-calf pairs.

Evolutionary Significance We examined the evolutionary significance of dorsal markings by comparing the reproductive success of animals with and without markings. Female reproductive success was assessed by comparing age at first calving, calf size, calving intervals, and length of sighting history. Right whales generally calve once every 3 years, but both shorter and longer intervals have been observed (Best 1990; Payne et al. 1990). It is difficult to separate longer calving intervals that result from increased time periods between pregnancies from those that result from a calf being produced during the intervening years but not seen. To compensate for this difficulty we calculated mean calving intervals for all interval data and also for 2- to 5-year intervals only. Male success was estimated by comparing the frequency distribution of markings in calves with the frequencies expected based on noncalf frequencies and panmix- ic mating. For these calculations, all grey- morph adults were assumed to be males. Figure 2. Grey-morph right whale photographed as (A) a calf and (B) a 2-year-old. (Photographers: G. Harris Since some of these adults may be fe- and R. Payne) males, the predicted frequencies will pro- vide maximum estimates of grey-morph primer, and 0.4 units of BIOLASE DNA on white-blaze and partial-grey-morph male success. We also compared lengths polymerase). Following denaturation at calves; although the latter are white in of sighting histories of grey-morph and 94ЊC for 2 min, each reaction mixture was calves, they are larger than the white blaz- black males. subjected to 34 cycles of 94ЊC for 60 s, es and the two have very distinctive 52ЊC for 60 s, and 72ЊC for 90 s. Negative shapes (Table 1; Figures 1 and 2). In con- controls (no template) were included in trast, grey-morph animals with white blaz- Results each experiment to detect any contami- es exist, but the relative frequency of such Sexing nating DNA. PCR products were sized by animals remains uncertain due to the dif- electrophoresis through a 3% NuSieve௢ Skin samples were obtained from 97 ani- ficulty of detecting white blazes in young gel. Each animal was sexed twice. mals including 60 with dorsal skin mark- grey-morph animals in aerial photographs. ings. Sampled whales included 25 animals Modes of Inheritance Consequently, although six categories ex- (19 females and 6 males) whose sex was Most of the dorsal skin color patterns are ist, we did not attempt to separate grey- identified behaviorally and/or morpholog- easy to distinguish, including the marks morph animals with a white blaze from ically as well as genetically (Table 2). All

466 The Journal of Heredity 1999:90(4) Table 2. Relative frequency of marks among Table 3. Relative frequencies of dorsal skin type (no equivalent amont hemizygous genetically sexed animals color marks males), and XGXG and XGY causing the black Marking Males Females Marking Noncalves Cows Calves skin color. Both males and females displayed white Black 18 19 A. Population off South Africa blazes including partial-grey-morph fe- White-blaze 8 6 Black N/A 84.3%a 89.3%b Partial-grey-morph 0 28 White-blaze N/A 4.8%a 1.5%b males (Tables 2 and 3) and grey-morph Partial-grey-morph Partial-grey- males (observed in Argentina population). with white blaze 0 4 morph N/A 9.1%a 5.6%b Grey-morph 14 0 Partial-grey- Sighting data indicated that the propor- morph with tion of white-blaze animals was similar white blaze N/A 1.4%a 0.2%b among cows and noncalves off Argentina a b Grey-morph N/A 0.3% 3.5% (Table 3). If noncalves exhibit a 1:1 sex ra- genetic sex assignments agreed with those B. Population off Argentina tio, then these results suggest that the c d e assigned in the field. Black 93.1% 92.0% 93.7% white blaze occurs with equal frequency White-blaze 2.8%c 2.6%d 2.0%e Partial-grey- among both sexes. Both white-blaze and Modes of Inheritance morph 2.6%c 4.7%d 3.2%e black calves were produced by cows with All five phenotypes were present in both Partial-grey- morph with and without a white blaze (Table 4). These populations (Table 3). The black pheno- white blaze 0.2%c 0.6%d 0.1%e patterns are consistent with the white type was the most common in both pop- Grey-morph 1.3%d,f 0.0%d 1.0%e blaze being a simple autosomal trait. ulations, but the population off South Af- If a simple genetic system is assumed, a N rica had a significantly lower proportion of ϭ 351. b N ϭ 1026. then it is possible to investigate whether black animals than did the population off c N ϭ 1048. the black or the white-blaze phenotype is Argentina (black versus nonblack, G1 ϭ d N ϭ 340. dominant using the Hardy–Weinberg equa- 62.72, P Ͻ .0001). e N ϭ 730. tion (p2 ϩ 2pq ϩ q2 ϭ 1). This calculation If the dorsal markings are autosomal f One non-calf and one calf were grey-morphs that also requires that the population be in Hardy– traits, then the marks should be equally had a white blaze. Weinberg equilibrium (i.e., relative fre- common in males and females and marked quency of alleles remains the same from calves should be produced by both white-blaze cows (Table 4). These patterns generation to generation; Ayala 1982). The marked and unmarked cows. If X-linked, suggest that the partial-grey-morph and relative frequency of white-marked ani- we would expect the proportion of marked grey-morph phenotypes are controlled by mals differed significantly for cows and versus unmarked animals to differ be- one gene and the white-blaze phenotype by calves off South Africa (cows versus tween males and females, with males ex- another. Given that the grey-morph trait calves: G ϭ 16.107, P Ͻ .01) indicating that hibiting the recessive phenotypes more has three phenotypes (grey-morph, partial- the assumptions required for Hardy–Wein- frequently than females. grey-morph, and black), one of which (par- berg equilibrium were not met by this pop- Among genetically sexed individuals, all tial-grey-morph) appears to be sex-specific, ulation. The relative frequencies among an- partial-grey-morph animals were females, and given that males exhibited the grey- imals off Argentina did not differ signifi- regardless of whether they had a white morph phenotype much more frequently cantly (cows versus calves: G ϭ 1.985, P blaze as well (N ϭ 32). Sighting data from than did females, this trait is probably X- ϭ 0.32; noncalves versus calves: G ϭ 2.68, Argentina indicated that partial-grey- linked, with genotypes XgXg and XgY pro- P ϭ 0.32). For this reason, only the Argen- morph animals (with and without white ducing the grey-morph phenotype, XGXg tina sample was used in this analysis. blazes) were approximately twice as com- producing the partial-grey-morph pheno- If white blazes are the dominant phe- mon among cows (5.3%, N ϭ 340) as among calves (3.3%, N ϭ 730) and noncalves (2.8%, N ϭ 1048); if calves and non- Table 4. Cow-calf inheritance patterns for dorsal color markings calves exhibit a 1:1 sex ratio, then these results are consistent with partial-grey- Calves morph animals being female. Partial-grey- Partial- Partial- grey with morph animals off South Africa were also White- grey white Grey- approximately twice as common among Cows Black blaze morph blaze morph Total cows as among calves (10.5%, N 351, ϭ A. Population off South Africa versus 5.8%, N ϭ 1026) (data for non- Black 788 10 30 1 0 829 calves not available). White-blaze 55 3 1 0 0 59 All grey-morph animals sexed genetically Partial-grey-morph 50 1 22 0 31 104 Partial-grey morph with were male (N ϭ 14). The proportion of white 8 1 3 1 2 15 grey-morphs observed among calves and Grey-morph 0 0 0 0 2 2 noncalves off Argentina were similar (Table Total 901 15 56 2 35 1009 3; G ϭ 0.536, P ϭ .464; South African non- B. Population off Argentina calf data not available), whereas grey- Black 636 11 17 1 0 665 White-blaze 20 4 0 0 0 24 morph cows were rare or absent in both Partial-grey-morph 24 0 6 0 6 36 populations (Table 3). Grey-morph calves Partial-grey morph with were produced by grey-morph cows and by white 4 0 0 0 1 5 Grey-morph 0 0 0 0 0 2 partial-grey-morph cows with and without Total 684 15 23 1 7 730 white blazes but not by black cows or

Schaeff et al • Right Whale Dorsal Markings 467 notype, then at least half of the calves pro- Table 5. Comparison of population parameters for right whales with different coloration patterns duced by white-blaze females should also Dorsal skin color marking be white-blaze. This prediction is not sup- ported by cow-calf transmission patterns Black White-blaze Partial-grey Grey-morph

(cowwhite-blaze/calfwhite-blaze observed: 13.8%, N A. South African population ϭ 29; expected: Ն50%; G ϭ 9.01, P ϭ .03). Cows In contrast, if the white blazes are re- Calving interval (years) 3.6 Ϯ 1.38 (539)a 3.8 Ϯ 1.70 (37)a 3.3 Ϯ 0.81 (69)a n/a 3.1 Ϯ 0.52 (473)b 3.1 Ϯ 0.51 (30)b 3.2 Ϯ 0.57 (66)b n/a cessive, then the proportion of white- Calf length (m) 6.87 Ϯ 0.98 (131) 6.99 Ϯ 0.80 (12) 7.42 Ϯ 0.78 (5) n/a blaze offspring produced by white-blaze Age at 1st calving (years) n/a 8.25 Ϯ 2.63 (4) 8.79 Ϯ 2.17 (19) n/a cows should equal the probability that a Sighting history (years) 9.2 Ϯ 4.23 (243) 11.7 Ϯ 3.50 (10) 9.4 Ϯ 4.18 (33) n/a male will pass on a recessive allele: Adult males Sighting history (years) n/a n/a n/a n/a

cowwhite-blaze /calfwhite-blaze: B. Argentinean population Cows % expected q2 0.5(2pq), (1) ϭ ϩ Calving interval (years) 4.7 Ϯ 2.53 (347)a 4.4 Ϯ 2.29 (19)a 3.5 Ϯ 1.15 (20)a n/a b b b 2 3.3 Ϯ 0.71 (245) 3.0 Ϯ 0.41 (13) 3.3 Ϯ 0.83 (19) n/a where q is the population frequency of Calf length (m) n/a n/a n/a n/a white-blaze adults. Similarly, if recessive, Age at 1st calving (years) 11.26 Ϯ 2.79 (19) 12.0 (1) 9.20 Ϯ 1.79 (5) n/a then the proportion of white-blaze calves Sighting history (years) 9.77 Ϯ 5.29 (186) 11.67 Ϯ 6.50 (6) 9.50 Ϯ 4.93 (8) n/a produced by black cows is the probability Adult males that the cow is heterozygote and passes Sighting history (years) 9.15 Ϯ 5.35 (27) 6.50 Ϯ 0.71 (2) — 5.86 Ϯ 4.02 (7) on her recessive allele times the probabil- Mean Ϯ SD; numbers in parentheses are sample sizes. ity that males will pass on a recessive al- a All intervals. lele: b 2- to 5-year intervals. Statistics: calving intervals: all intervals: ANOVA: (partial-grey-morph/not, white-blaze/no white-blaze: a) F ϭ cow /calf : 1,1,1 black white-blaze 0.758, P ϭ .38, Bonferroni/Dunn: all insigniﬁcant at 0.05 level; b) F1,1,1 ϭ 0.771, P ϭ .38, Bonferroni/Dunn: all insig-

nificant at 0.05 level; 2- to 5-year intervals: a) F1,1,1 ϭ 0.179, P ϭ .18, Bonferroni/Dunn: all insignificant at 0.05 level; 2 % expected ϭ [q ϩ 0.5(2pq)] b) F1,1,1 ϭ 0.004, P ϭ .95, Bonferroni/Dunn: all insignificant at 0.05 level; calf length (black calves): a) ANOVA (length, month): partial-grey morph and black cows only (white-blaze cows, N too small to include) F3,3 ϭ 0.861, P ϭ .46; ϫ [0.5(2pq)/( p2 ϩ 2pq)]. age at first calving: a) partial-grey morph versus white-blaze: t test: t ϭ 1.56, P ϭ 13; b) black versus partial-grey morph: t test: t ϭ .56, P ϭ .13; sighting history: a) cows: ANOVA (color) F2 ϭ 1.741, P ϭ .18, Bonferroni/Dunn: all

(2) insigniﬁcant at 0.05 level; b) cows and adult males: ANOVA (sex, color) F1,2 ϭ 556, P ϭ .57, Bonferroni/Dunn: all insigniﬁcant at 0.05 level. Distribution of dorsal markers among cow- calf pairs off Argentina were consistent with both of these predictions (cowwhite-blaze/ cows and calves, which increases the among partial-grey-morph and white-blaze 2 calfwhite-blaze observed: 13.8%, N ϭ 29; if q ϭ probability of type II errors) (South Afri- cows off South Africa did not differ (Table 3.0%, then expected: 17.2%; G ϭ 0.132, P ϭ can data could not be analyzed because 5).

.717; and cowblack/calfwhite-blaze observed: grey-morphs could not be distinguished Black calves produced by partial-grey- 1.7%, N ϭ 713 versus expected: 2.5%; G ϭ from grey-morphs with white blazes). morph and black cows had comparable 1.22, P ϭ 0.27). Thus transmission patterns We conclude that the two-gene model mean body lengths (Table 5), as did par- between cows and their offspring off Argen- (X-linked grey-morph, white-blaze reces- tial-grey-morph and black calves produced tina are consistent with the white-blaze sive autosomal) provides an excellent ﬁt by black cows (South Africa, partial-grey- phenotype being recessive (ww) to the no- to all the available data for both southern morph calves: 6.66 Ϯ 1.13, N ϭ 7 versus white-blaze (black) phenotype (Ww, or right whale populations. all-black calves: 6.90 Ϯ 0.993, N ϭ 133; AN-

WW). OVA: length and month measured, F0,3 ϭ If the white-blaze trait is inherited in- Evolutionary Significance 0.769, P ϭ .51; Argentina: data unavail- dependently of the grey-morph trait, then There was no significant difference in ob- able). Lengths of sighting histories were the ratio of partial-grey-morph and grey- served calving intervals for partial-grey- also similar for partial-grey-morph and morph animals with and without the white morph versus black cows within either black cows (Table 5; t ϭ 0.144, P ϭ .886); blaze should be the same as that for ani- population (all intervals or 2- to 5-year in- because grey-morph cows were very rare, mals without the grey-morph trait (black) tervals only; Table 4). Mean calving inter- there were insufficient data to include with and without the white blaze. Similarly vals were shorter among cows off South these cows in the analyses. the proportion of white-blaze animals with Africa than those off Argentina, but inter- Grey-morph females (XgXg) result from and without the grey- or partial-grey- population differences in parameters such matings between grey-morph (XgXg) or morph should be the same as non-white- as calving intervals and age at sexual ma- partial-grey-morph (XGXg) females and blaze animals (black) with and without turity are not valid because they assume grey-morph males (XgY). The number of the grey-morph trait. Distribution of mark- that survey efficiency is comparable be- grey-morph females expected in the pop- ings among right whales off Argentina did tween populations, which is highly unlike- ulation is the probability that a female will not differ significantly from that expected ly. contribute a recessive allele times the if the grey-morph and white-blaze traits Among right whales off Argentina, par- probability that a male will contribute a segregated independently (Calves: G tial-grey-morph cows tended to be youn- ϭ recessive allele: 0.352, P ϭ .55; noncalves: G ϭ 1.75, P ϭ ger at first calving than black cows, but .19; cows: G ϭ 2.427, P ϭ 0.12; the expect- the difference was not significant (Table g g 2 X X ϭ [qadult female ϩ 0.5(2pq)] ed frequencies of animals with both traits 5). Data were unavailable for black cows were very low for all three tests, Ͻ1.0% for off South Africa; mean age at first calving ϫ (0.5qadult male). (3)

468 The Journal of Heredity 1999:90(4) Applying this formula, two of the 1009 2.29, P ϭ 0.140). Sighting histories of all in this article explains grey-morph females right whale calves produced off South Af- animals with the grey-morph trait (male as XgXg homozygotes. Since such females rica between 1979 and 1992 should have grey-morphs and female partial-grey- would transmit an Xg chromosome to ev- been grey-morph females (one observed; morphs, 7.80 Ϯ 4.15, N ϭ 15) did not differ ery one of their offspring, they should pro- g G qadult male estimated by qcalf male) and 0.2 of significantly from those of all black ani- duce mainly partially grey-morph (X X ) the 730 calves produced off Argentina be- mals (male and female, 9.70 Ϯ 5.29; t ϭ daughters and grey-morph (XgY) sons. (At tween 1971 and 1990 should have been 1.35, P ϭ .18). Sighting history data were low frequencies they would also produce grey-morph females (none observed). unavailable for male right whales off South XgXg grey-morph females like themselves.) South African sighting data indicated that Africa. Such females are not expected ever to pro- partial-grey-morph animals occurred in White-blaze and black cows exhibited duce black offspring of either sex. groups with grey-morph animals as often similar calving intervals, mean calf body How can the two black offspring of grey- as expected based on the relative frequen- lengths, and length of sighting histories morph mothers be explained? There are cy of the two types of animals in the pop- (Table 5). Nonetheless, the proportion of several possibilities. In principle, better ulation (mean number of animals ob- white-blaze animals was lower among photographs might reveal small gray blaz- served in groups, excluding cow-calf pairs, calves than adults in both populations es on the poorly imaged extremities (or was 2.96 Ϯ 1.36 animals/group, N ϭ 122, (South Africa: calves 1.7% versus cows undersides) of the two apparently ‘‘black’’ range 2–8 animals; groups with both a par- 6.2%, G ϭ 16.107, P Ͻ .01; Argentina: calves, or these calves might not be off- tial-grey-morph and grey-morph animal: calves 2.1% versus cows 3.2%, G ϭ 0.985, spring of the grey-morph individuals they observed 4/122 groups, expected 4.7/122; P ϭ .32; versus noncalves 3.0%, G ϭ 1.00, were near when photographed. These ar- G ϭ 0.116, P ϭ 0.73). P ϭ .32). The expected proportion of tifactual explanations seem unlikely. Tak- The production of partial-grey-morph white-blaze calves (ww) produced by ing the observations at face value, models calves (XGXg) by black females (XGXG) in- white-blaze cows (ww) equals the proba- involving partial penetrance or X-inacti- dicates that grey-morph males (XgY) are bility that a male will contribute a reces- vation can be constructed to explain how fertile (Table 4). The expected proportion sive allele times the males’ success in XgXG females might occasionally exhibit of partial-grey-morph calves produced by achieving fertilization: grey-morph and/or black phenotypes. An black cows equals the probability that a even simpler model is one in which the cow /calf : grey-morph male will contribute his X white-blaze white-blaze South African population contains a third chromosome times his success in achiev- % expected ϭ [q2 ϩ 0.5(2pq)](s), (5) type of X chromosome, XD, in which a re- ing fertilizations: gion that includes the G locus is deleted. where s is the success of males that carry XgXD females would be effectively hemizy- cowblack /calfpartial-grey morph: the recessive allele compared to that of gous, like XgY males, and would therefore males who do not carry the recessive al- be grey-morph, and some of their off- % expected ϭ (0.5qadult male)(s), (4) lele (because data for noncalves were un- spring would be black (XGXD) females. where s is the albino males’ success in available, q2 for South Africa was calculat- Additional observations will be needed achieving fertilizations relative to that of ed from cow frequencies; South Africa: if s to distinguish among these alternative black males. Among right whales off Ar- ϭ 100%, G ϭ 9.154, P ϭ .002; if s ϭ 70%, G models. The discovery of black calves pro- gentina, the observed frequency of partial- ϭ 4.19, P ϭ .041; if s ϭ 69%, G ϭ 3.36, P ϭ duced by grey-morph mothers does not grey-morph calves produced by black .067; Argentina: if s ϭ 100%, G ϭ 0.133, P warrant wholesale rejection of the basic cows (i.e., black without white blaze: XGXG, ϭ .72). If the white blaze allele is com- sex-linked model for control of grey- W- and black with white blaze: XGXG, ww) pletely recessive to the black allele, then morph and partial-grey-morph pheno- was not significantly different from the although both heterozygous and homozy- types, because the model gives such a number expected if grey-morph males ex- gous recessive males contribute recessive good fit to the bulk of the data. perienced 100% reproductive success rel- alleles, only homozygous recessive males ative to black males (observed 18/665 if will experience any phenotypic effects. ϭ Discussion s ϭ 100%, expected ϭ 9/665, G ϭ 3.12, P Since homozygous recessive animals are ϭ .08). A population estimate for adult relatively rare in the population (South Af- Five dorsal skin color phenotypes are male grey-morph males was not available rica: ww ϭ 0.03 versus Ww ϭ 0.346), the present in right whale populations off for right whales off South Africa; estimates impact per ww male would have to be South Africa and Argentina (Best 1990; great to account for the observed reduc- based on qmale calves indicated no difference Payne et al. 1983; this study). Field and ge- between observed frequency (31/829) and tion. netic data from these populations show that expected if males experienced 100% similar general trends, suggesting that the success relative to black males (29/829; G Note Added in Proof modes of inheritance are the same in the ϭ 0.069, P ϭ .79). two populations. The grey-morph trait ob- Among right whales off Argentina, mean Recent additions to the catalog of South served among right whales (grey-morph, length of sighting history was comparable African right whales (subsequent to the partial-grey-morph, and black phenotypes, for black males (9.15 Ϯ 5.35 years, N ϭ 27) analysis presented in Table 3) indicate a previously known as partial albino, grey- and black females (9.77 Ϯ 5.29 years, N ϭ total of three grey-morph individuals (pre- blaze, and black, respectively; Best 1990; 186; t test: t ϭ 0.574, P ϭ .57). Grey-morph sumably females) that have been photo- Payne et al. 1983) appears to be an X- males exhibited shorter sighting histories graphed with a total of eight calves. Six of linked gene with a female-specific partial- (5.86 Ϯ 4.02 years, N ϭ 7) than did black these calves are grey-morphs, but two (as- grey-morph phenotype resulting from males, but the difference was not signifi- sociated with two different adults) appear the heterozygote genotype (hemizygous cant given current sample sizes (t test: t ϭ to be entirely black. The model developed males do not exhibit the phenotype).

Schaeff et al • Right Whale Dorsal Markings 469 Since partial-grey-morph female calves that grey-morph males are as successful with partial albinism in both Tietz’s syn- have areas with black pigment and areas as black males in achieving fertilizations drome and Ziprkowski’s trait (Searle without pigment (similar to the lack of pig- with black cows. Grey-morph males may 1968). Right whale courtship behavior is ment observed in grey-morph calves), this exhibit shorter sighting histories than do thought to be initiated by female vocali- phenotype may be the result of X-inacti- black males, but the difference was not zations (Kraus 1991). Given the reproduc- vation patterns (i.e., one of the female’s significant given current sample sizes. Ad- tive success of male grey-morphs (ob- two X chromosomes is deactivated in ditional data are required to further inves- served participation in right whale court- each cell, resulting in some cells exhibit- tigate the impact of dorsal color patterns ship groups and proportion of partial- ing one phenotype and others the second on male fitness. grey-morph calves produced by black phenotype—mosaicism or Lyon’s hypoth- The proportion of white-blaze animals is cows), it is unlikely that these males are esis; Weaver and Hedrick 1992). The white lower among calves than adults in both suffering from severe deafness. blaze phenotype appears to be inherited populations, significantly so among South It is not clear why grey and partial-grey- independently of the grey-morph trait and African animals. Comparisons of observed morph right whales gradually darken with to be a recessive autosomal trait. This and expected frequencies of white-blaze age. The dominant alleles of the roan (R) two-gene model gives an excellent fit to all calves produced by white-blaze cows sug- and ticking (T) genes cause dog coat col- available data for both populations of gest that white-blaze males off South Afri- ors to darken (Searle 1968), and tempera- southern right whales. ca may be less successful in achieving fer- ture-dependent darkening is common in Although many skin color mutations are tilizations than are black males (s Ͼ 70%). Himalayan mice, rabbits, and cats. As well, associated with pathological pleiotropism In contrast, white-blaze and black males a slow spread of pigmentation from pig- (Copeland et al. 1990; Goulding et al. 1993; off Argentina appear to experience similar mented areas to nonpigmented ones has Hosoda et al. 1994; Jackson 1997; Moller et levels of success. In addition to differenc- been observed in guinea pigs, cattle, al. 1996), we found no evidence to suggest es in male reproductive success, some of sheep, pigs, and Dalmatians (Searle 1968). that any of the dorsal skin color patterns the discrepancy in the proportions of Additional data are required to further ex- observed in these right whales are corre- white-blaze animals within and between amine the issue in right whales. lated with a reduction in the reproductive populations could be the result of adults Recently Portway et al. (1998) deter- success of cows. Calving intervals were being scored as white-blaze due to scars mined that despite the lack of physical similar for partial-grey-morph, white-blaze, they acquired since they were sighted as barriers between geographic areas, the and black cows in both populations sug- a calf, of white blazes on calves being level of mtDNA gene flow is limited be- gesting that all cows are equally fertile. missed if the blazes were positioned low tween the wintering populations of right Calves produced by partial-grey-morph on the back (South Africa), and of calves whales off Argentina and South Africa. The and black cows off South Africa had simi- being less well photographed than cows— different relative frequencies of both types lar mean body lengths (white-blaze cows’ the backs of many calves cannot be seen of dorsal color markings observed in the data unavailable; Argentinian data unavail- clearly because the calves remain under- two populations suggests that nuclear able) and the relative proportion of par- water (Argentina). Hence any potential gene flow may also be limited. However, tial-grey-morph and white-blaze animals correlation between the white-blaze dor- given the low frequency of the nonblack among calves and noncalves suggests that sal mark and male reproductive success is phenotypes in the populations, the useful- neither category of marked animals expe- difficult to judge. ness of these markers for detecting gene rienced increased juvenile mortality. In ad- Anomalously white individuals have flow is relatively limited. Analysis with a dition, partial-grey-morph, white-blaze, and been observed in 20 cetacean species more sensitive marker, such as microsat- black cows had sighting histories of simi- (Fertl et al., in press; Hain and Leather- ellites, needs to be performed to estimate lar length and exhibited similar ages at wood 1982), but southern right whales are the extent of gene flow. first calving. Small sample sizes for some the only species where such individuals In addition to the two populations of categories in some of the analyses weak- are relatively common. A number of forms southern right whales described in this ened the strength of the analyses. How- of partial albinism have been identified in study, all five phenotypes have been ob- ever, since the results from all five analy- other mammals, including three which served among southern right whales off ses are consistent with there being no dif- may be X-linked: (1) the mottled gene se- Australia (Bannister J and Burnell S, per- ference in cows’ fitness, there are ample ries first described by Fraser et al. (1953), sonal communication) and New Zealand data overall to support this hypothesis. (2) Tietz’s syndrome (Tietz 1963), and (3) (Patenaude et al. 1998). In contrast, none Grey-morph cows (XgXg) are rare and so a recessive X-linked trait described by of the northern right whales in the west- are not included in the above analyses. Ziprkowski et al. (1962). However, none of ern North Atlantic display dorsal markings Given the low population frequencies of these genes have patterns of inheritance (Schaeff and Hamilton, in press) and only the grey-morph (XgY) and partial-grey- and expression similar to those associated the white dorsal blaze has been observed morph phenotypes (XGXg), few homozy- with grey-morph in right whales. For ex- among the North Pacific right whales gote recessives are expected in either pop- ample, hemizygous mottled males are in- (Herman et al. 1980; Rowntree et al. 1980). ulation. Hence it appears that grey-morph viable, as are many of the homozygous The failure to observe North Pacific ani- females are not missing but simply rare. mottled females. Both Tietz’s syndrome mals with the grey-morph or partial-grey- The occurrence of grey-morph females and Ziprkowski’s trait lack heterozygotic morph phenotypes could be due to the and the production of partial-grey-morph mosaicism and, in contrast to the situa- small number of individuals sighted, a low- calves by black cows indicates that grey- tion in right whales, the white phenotype er allele frequency in this population, or morph males are fertile. As well, compar- does not darken with age in any of these to the allele being absent. Observed dif- ison of observed and expected frequen- three forms of X-linked partial albinism. Fi- ferences in the frequencies of dorsal pig- cies of partial-grey-morph calves suggests nally, complete deafness is associated mentation patterns between the northern

470 The Journal of Heredity 1999:90(4) and southern hemispheres suggest that Fertl D, Pusser LT, and Long JJ, in press. First record port of the International Whaling Commission, Special of an albino bottlenose dolphin (Tursiops truncatus) in Issue Selected Symposium 76, Whales. Boulder, Colo- gene flow across the equator may be lim- the Gulf of Mexico, with a review of anomalously white rado: Westview Press; 371–445. cetaceans. Mar Mamm Sci 15. ited and thus provides support for the hy- Payne R, Rowntree VJ, and Perkins JS, 1990. Population pothesis that northern (E. glacialis) and Fraser GR, Sobey S, and Spicer CC, 1953. Mottled a sex- size, trends and reproductive parameters of right southern (E. australis) right whales are re- modified lethal in the house mouse. J Genet 24:217–221 whales (Eubalaena australis) off Peninsula Valdes, Ar- [as cited by Searle (1968)]. gentina. 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Schaeff et al • Right Whale Dorsal Markings 471