Seasonal Changes in Supraorbital Comb Characteristics and Fecal Testosterone Levels in Captive Male Svalbard Rock Ptarmigans (Lagopus Muta Hyperboreus)
Research note Reproduction
Seasonal Changes in Supraorbital Comb Characteristics and Fecal Testosterone Levels in Captive Male Svalbard Rock Ptarmigans (Lagopus muta hyperboreus)
Saori YAMAMOTO1), Satoshi KUSUDA1, 2)*, Masaharu HORIGUCHI3), Yuji ISHIHARA3) and Osamu DOI1, 2)
1)The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. 2)Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. 3)Toyama Municipal Family Park Zoo, 254 Furusawa, Toyama 930-0151, Japan.
［Received 14 November 2015; accepted 8 April 2016］
ABSTRACT The comb is a good indicator of physical condition in male birds. We monitored the seasonal changes in supraorbital comb characteristics with visual assessments and fecal testosterone concentrations by enzyme immunoassay in three captive male Svalbard rock ptarmigans (Lagopus muta hyperboreus). Although there were interindividual variations, the size and redness increased from February to August; i.e., before and during breeding season. The fecal testosterone levels increased markedly between May and June, and declined sharply from late June. The color simultaneously changed from deep to pale red but size was kept until testosterone concentrations fell to baseline. We suggest that changes occurring in supraorbital comb, especially its redness, reflect testicular activity and may be useful indicators for captive breeding of this species. Key words: Supraorbital comb, Svalbard rock ptarmigan, Testosterone － Jpn J Zoo Wildl Med 21（2）：41-45，2016
Tetraonidae birds, belonging to order Galliformes, have a relationship between T levels and comb has been detected in supraorbital comb, which acts as a secondary sexual trait, Tetraonidae birds. T treatment induced comb growth in willow and the characteristics of the comb are strongly related to ptarmigans (Lagopus lagopus lagopus) even though the birds reproductive success. Sexual ornamentation (the color, length, had been kept in short day conditions [6]. Stokkan [7] reported and size of the comb in males) and the role of testosterone that comb growth is directly dependent on T levels and (T) have been studied in male red jungle fowl (Gallus gallus) indirectly related to day length in willow ptarmigans. Studies and domestic fowl (G. domesticus) species [1-3]. In birds, of male willow ptarmigans have indicated that plasma T levels comb is usually more conspicuous in males than in females control comb expression [8] and that mating male willow [4]. Accumulating evidence suggests that fleshy comb plays ptarmigans have larger combs than unmating territorial males; a prominent role as a sexual signal in male red jungle fowl, however, the comb sizes of polygynous and monogamous but Parker and Ligon [5] indicated in their recent review that males did not differ [9]. In addition, T might also regulate the influence of T on comb growth is dependent on bird’ s immune function, as suggested by the immunocompetence physical condition (such as health and immune function). In handicap hypothesis [10], which proposes that males who addition, comb acts as an important signal during male-male can afford to reduce the quality of their immune systems are competition and impacts on mate choice by females [1]. A able to express exaggerated sexual traits. In a previous study, T treatment had positive effects on the reproduction of red grouse (L. lagopus scoticus), e.g., it increased the birds’ comb
* Corresponding author： size and competitive ability, whereas their weight decreased Satoshi KUSUDA（E-mail: [email protected]） and they were carrying more parasites [11]. Female birds
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Small(1) Medium(2) Large(3)
Figure 1 Heads of male Svalbard rock ptarmigan showing supraorbital combs. The size of comb was visually evaluated using the following scoring system: 1 = small, 2 = medium, and 3 = large. Redness of combs was classified as either pale or deep. prefer males with outstanding sexual traits because they infer was employed from mid-May to July, and minimal lighting (15.5 that such males have genes that enable their chick to resist h dark: 8.5 h light) was provided from December to February. parasite infections [12]. Thus, the combs of male birds might During the intervening periods, light exposure was increased or be indicative of their reproductive ability and immune status. decreased at approximately 2-week intervals. The birds had ad To extrapolate, reproductive hormonal status based on the libitum access to rabbit food pellets, Japanese mustard spinach appearance of external structures, such as comb or wattle [4], (Brassica rapa var. perviridis), and water. Morphological may help captive breeding, especially during the pairing of changes in the supraorbital comb were visually assessed in male with female in preparation for the reproductive season. all three males by the same zookeeper twice a month (usually The purpose of our study was to evaluate the relationships on the 1st and 15th days of each month). Supraorbital comb between supraorbital comb characteristics and T concentrations size was visually evaluated using the following scoring system: in male Svalbard rock ptarmigans (L. lagopus hyperboreus). We 1 = small, 2 = medium, and 3 = large (Fig.1). Supraorbital used fecal samples for the hormonal assays, which enabled us comb redness was classified as pale or deep. Excreted fecal to perform longitudinal monitoring in a non-invasive manner. samples were collected from two males (No. S53 and S65) on Three male ptarmigans (studbook No. S53, S65, and S85; 1-4 days/week. The sampling period lasted from January 3 the birds were 2.5, 1.4, and 1.4 years of age at the start of the to November 13, 2012, for No. S53 and from December 20, experiment) used in this study were kept at Toyama Municipal 2011, to June 25, 2012, for No. S65. One ptarmigan (No. S65) Family Park. Each bird was kept in a wire cage under died unexpectedly on June 28, 2012.The samples were stored controlled lighting conditions, as described in our previous at -20oC until hormone analysis. Each fecal sample was dried, study [13]. Maximum continuous lighting (0 h dark: 24 h light) and T was extracted using the methanol extraction method
1
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3 500 3 500 S53 S65 400 400 2 2 300 300
200 200 1 1 100 100 Fecal teststerone(ng/g) 0 0 Fecal teststerone(ng/g) 11 12 1 2 3 4 5 6 7 8 9 10 11 0 11 12 1 2 3 4 5 6 7 8 9 10 11 0
Supraorbital comb size score 2011 2012 Supraorbital comb size score 2011 2012 3 S85 Figure 2 Seasonal changes in supraorbital comb status and fecal testosterone (T) concentrations in male Svalbard rock 2 ptarmigans The bar graph shows the supraorbital comb status of 1 individuals No. S53, S65, and S85. The heights of the bars indicate each individual’s comb size score. The colors of the bars indicate the color intensity of the comb: white, pale red; gray, deep red. The line graph shows the fecal T concentrations 0 11 12 1 2 3 4 5 6 7 8 9 10 11 (month) 2011 2012 (year) ( ± SE) of individuals No. S53 and S65. The T concentrations Supraorbital comb size score represent the mean values for the periods from day 1 to day 15 or from day 16 to the end of the month. The open circle indicates that the sample is less than three. [14]. Fecal T concentrations were assayed by an enzyme immunoassay, as reported previously [14]. The T values for No. S53 and S65 represent the mean concentrations for the period as its fecal T concentrations fell, producing an annual cycle. from day 1 to day 15 (the first half of the month) or from day Thus, we infer that changes in comb color are a sensitive 16 to the end of the month (the second half of the month). marker of circulating T levels, which in turn are indicative of Figure 2 shows the changes in the supraorbital comb status fluctuations in testis activity. In No. S85 bird, the comb became of all three males (No. S53, S65, and S85) studied and the bigger and its color became more intense later than in No. S53 changes in fecal testosterone concentrations for two males (No. (Fig. 2). Specifically, No. S85 first demonstrated a comb size S53 and S65). In No. S53 bird, marked changes in the size and score of 3 on May 15 (compared with May 1 in No. S53), and redness of the supraorbital comb were noted on February 15 the color of the comb changed from pale to deep red on May 1 and March 15, respectively. The comb size score for No. S53 (compared with March 15 in No. S53). These differences might changed from 1 to 2 and then increased further to 3, and the have been related to the males’ social ranks because it has color of its comb also changed from pale to deep red. The fecal been reported that supraorbital comb height is correlated with T concentrations of No. S53 ranged from 24.23 ng/g in second social rank in willow ptarmigans [15]. However, it is unclear half of February (n=1) to 388.03 ng/g in second half of May whether social hierarchy among individuals do exist, as these (n=8) (Fig. 2). This bird’ s fecal T levels started to increase in birds were kept in cages individually. Moreover, existence in April and peaked in late May. Changes in the color of No. S53’s the difference of fecundity related age cannot be ignored. In supraorbital comb occurred simultaneously with the increase red jungle fowl, used for male-male staged fights, older males in its fecal T concentration. The fecal T concentrations of No. (2-year old and above) had significantly longer spurs than S53 fell markedly in late June, and its comb color became 1-year old males [1]. Svalbard rock ptarmigans can breed from paler. However, No. S53 continued to exhibit a comb score of yearling age. The birds used in this study were 2.5 and 1.4 3 until July 15. In this bird, the supraorbital comb started to years old at the start of the examination and we monitored increase in size and change to deep red in the lead up to the their third and second breeding challenges. Difference in reproductive period, and a simultaneous rise in fecal T levels reproductive success between ages (1 to 4-year old) have been was also detected. The bird’s comb color switched to pale red reported in white-tailed ptarmigan (L. leucurus) and willow
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ptarmigan as well, with older females exhibiting high fecundity Svalbard rock ptarmigans had in captivity, and the color of the than 1-year old females [16]. These variations may be related comb offers a good indication of testicular regression. These the breeding condition too. Thus, results obtained in this findings may aid decision-making regarding the timing of male study also may reflect the age difference; further research is and female pairing and assessments of the fertility potential necessary to confirm this inference. and general conditions of male ptarmigans kept in captivity. In No. S65 bird, changes in supraorbital comb size/redness This study was supported by the Tokyo Zoological Park and fecal T concentrations were not as marked (Fig. 2) as those Society Wildlife Conservation Fund. seen in No. S53 and S85. No. S65’s fecal T concentrations We acknowledge the assistance of Dr. Sachi Sri Kantha in ranged from 30.54 ng/g in second half of February (n=3) to improving the manuscript text. 172.26 ng/g in second half of May (n=8). As No. S65 died REFERENCES unexpectedly during the experimental period, we postulate that the factors that caused the bird’ s death might have had a 1. Ligon JD, Thornhill R, Zuk M, Johnson K. 1990. Male-male negative influence on the supraorbital comb changes. competition, ornamentation and the role of testosterone in Carotenoids also play a role in comb expression. For sexual selection in red jungle fowl. Anim Behav 40: 367-373. example, they are considered to affect coloration and self- 2. Zuk M, Johnsen TS, Maclarty T. 1995. Endocrine-immune maintenance (they buffer T-mediated immunosuppression), interactions, ornaments and mate choice in red jungle fowl. and the allocation of carotenoids is influenced by physiological Proc R Soc Lond B 260: 205-210. constraints [17]. Based on the variations seen in No. S65, 3. Verhulst S, Dieleman SJ, Parmentier HK. 1999. A tradeoff we consider that carotenoids are preferentially used for between immunocompetence and sexual ornamentation in immunohomeostasis rather than comb exaggeration. Thus, domestic fowl. Proc Natl Acad Sci USA 96: 4478-4481. the condition of the comb seems to provide information about 4. Owens IPF, Short RV. 1995. Hormonal basis of sexual immune status and general conditioning. dimorphism in birds: implications for new theories of sexual The condition and size of the supraorbital comb and T levels selection. Trends Ecol Evol 10(1): 44-47 . have been studied as characteristics associated with sexual 5. Parker TH, Ligon JD. 2007. Multiple aspects of condition selection and signaling in birds belonging to the Tetraonidae influence a heritable sexual trait: a synthesis of the evidence family [18-20]. Castrated male willow ptarmigans failed to for capture of genetic variance in red junglefowl. Biol J Linn show supraorbital comb growth even during photostimulation Soc 92: 651-660. [7]; however, supraorbital comb growth was induced in male 6. Stokkan KA. 1979. Testosterone and daylength-dependent red grouses that were implanted with T under the skin of development of comb size and breeding plumage of male their breasts [19]. In copulating male black grouses (Tetrao willow ptarmigan (Lagopus lagopus lagopus). Auk 96(1): tetrix), a significant positive relationship was detected 106-115. between supraorbital comb size and copulatory success, and 7. Stokkan KA. 1979. The effect of permanent short days and supraorbital comb size was significantly correlated with the castration on plumage and comb growth in male willow T level [18]. Thus, in Tetraonidae birds supraorbital comb ptarmigan (Lagopus lagopus lagopus). Auk 96(4): 682-687. expression is regulated by testicular hormones. 8. Stokkan KA, Sharp PJ. 1980. Seasonal changes in the In previous studies of Tetraonidae birds [8, 17, 18, 20], concentrations of plasma lutenizing hormone and T assays were carried out by collecting blood samples. In testosterone in willow ptarmigan (Lagopus lagopus lagopus) contrast, we assessed the utility of the supraorbital comb as with observations on the effects of permanent short days. a non-invasive external index of testicular activity by visually Gen Comp Endocrinol 40: 109-115. assessing the supraorbital comb and the changes in fecal 9. Hannon SJ, Eason P. 1995. Colour bands, combs and hormonal concentrations. The use of feces as an alternative to coverable badges in willow ptarmigan. Anim Behav 49: 53- blood is non-invasive and makes repetitive collection feasible. 62. As such, we suggest that the appearance of the supraorbital 10. Folstad I, Karter AJ. 1992. Parasites, bright males and the comb can be used as an indicator of testicular status in male immunocompetence handicap. Am Nat 139: 603-622.
－ 44 － Supraorbital comb and testosterone in male ptarmigan
11. Mougeot F, Redpath SM, Piertney SB. 2006. Elevated spring reproduction in white-tailed and willow ptarmigan Lagopus testosterone increases parasite intensity in male red grouse. leucurus and L. lagopus. IBIS 140: 14-24. Behav Ecol 17(1): 117-125. 17. Martínez-Padilla J, Mougeot F, Webster LMI, Pérez-Rodríguez 12. Hamilton WD, Zuk M. 1982. Heritable true fitness and L. 2010. Testing the interactive effects of testosterone and bright birds: a role for parasites? Science 218: 384-387. parasites on carotenoid-bases ornamentation in a wild bird. J 13. Yamamoto S, Kusuda S, Takahashi Y, Hori H, Horiguchi Evol Biol 23: 902-913. M, Ishihara Y, Doi O. 2015. Differences of hormone 18. Rintamäki PT, Höglund J, Karvonen E, Alatalo RV, Björklund concentrations and dynamics in rectal and cecal feces N, Lundbert A, Rätti O, Vouti J. 2000. Combs and sexual of captive Svalbard rock ptarmigan (Lagopus muta selection in black grouse (Tetrao tetrix). Behav Ecol 11: 465- hyperboreus). Jpn J Zoo Wildlife Med 20 (3): 51-55 (in 471. Japanese with English summary). 19. Mougeot F, Irvine JR, Seivwright L, Redpath SM, Piertney S. 14. Kusuda S, Morikaku K, Kawada K, Ishiwada K, Doi O. 2007. 2004. Testosterone, immunocompetence, and honest sexual Excretion patterns of fecal progestogens, androgen and signaling in male red grouse. Behav Ecol 15 (6): 930-937. estrogens during pregnancy, parturition and postpartum in 20. Martínez-Padilla J, Pérez-Rodríguez L, Mougeot F, Ludwig okapi (Okapia johnstoni). J Reprod Dev 53(1): 143-150. S, Redpath SM. 2014. Intra-sexual competition alters the 15. Gjesdal Å. 1977. External markers of social rank in willow relationship between testosterone and ornament expression ptarmigan. Condor 79: 279-281. in a wild territorial bird. Horm Behav 65: 435-444. 16. Wiebe KL, Martin K. 1998. Age-specific patterns of
研究短報 繁殖学
飼育下スバールバルライチョウ（Lagopus muta hyperboreus）における 眼窩上肉冠とテストステロン値の季節変化
山本彩織1），楠田哲士1, 2）＊，堀口政治3），石原祐司3），土井 守1, 2）
1）岐阜大学大学院連合農学研究科 〒 501-1193 岐阜県岐阜市柳戸 1-1 2）岐阜大学応用生物科学部 〒 501-1193 岐阜県岐阜市柳戸 1-1 3）（公財）富山市ファミリーパーク公社 〒930-0151 富山県富山市古沢 254
［2015 年 11 月 14 日受領，2016 年 4 月 8 日採択］
要 約 飼育下の雄スバールバルライチョウにおける眼窩上肉冠のサイズと赤さを目視により段階評価し，糞中テストステロン（T）含 量と比較した。夏の繁殖期に向けて肉冠のサイズと色の増強がみられ、同時にテストステロン含量は 5 月から 6 月に著しく増加 した。6 月末に T 含量の低下がみられ，肉冠は退色した。肉冠の変化は精巣活動を反映していることが示唆され，飼育下繁殖時の 個体管理に役立つ指標になると考えられた。 キーワード：スバールバルライチョウ，テストステロン，肉冠 －日本野生動物医学会誌 21（2）：41-45，2016
* 責任著者：楠田哲士（E-mail: [email protected]）
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