Comparison of physique and nutritional status between jungle crows trapped in Tokyo’s inner city and on the outskirts

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  • YOSHIHARA Masato
    Education and Public Relations Department, Tama Zoological Park United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology
  • SUZUKI Kaoru
    Field Science Center, Faculty of Agriculture, Tokyo University of Agriculture and Technology
  • KAJI Koichi
    Institute of Agriculture, Tokyo University of Agriculture and Technology

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Other Title
  • 都心と郊外のトラップで捕獲されたハシブトガラスの体格・栄養状態の比較
  • トシン ト コウガイ ノ トラップ デ ホカク サレタ ハシブトガラス ノ タイカク ・ エイヨウ ジョウタイ ノ ヒカク

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Abstract

<p>Jungle crows (Corvus macrorhynchos japonensis) were captured in the center (Ueno Zoological Gardens) and suburbs (Snow Brand’s Kodomonokuni Ranch) of Tokyo to survey regional differences in their physique and nutritional status. Analysis of sexual dimorphism revealed that, regardless of whether an individual was an adult or a juvenile, body mass was larger, the exposed culmen length was longer, and the bill height greater in males than in females at both Ueno and Kodomonokuni (P < 0.01). We then performed inter-regional comparisons of physique in both adults and juveniles separately according to sex. Body mass in all groups of birds studied (all adult males, all adult females, all juvenile males, and all juvenile females) was smaller at Ueno than at Kodomonokuni (P < 0.01). Conversely, in all groups, the bill (length of exposed culmen and height of bill)-a weapon in the struggle for survival (transport and securing of food, defense from the threat of attack by others)-was larger (P < 0.01) at Ueno than at Kodomonokuni. Individuals of either sex and any age at Ueno had poorer nutritional status (i.e. greater malnutrition rates) than those at Kodomonokuni (P < 0.01). Comparison of nutritional status between adults and juveniles revealed that juveniles at both Ueno and Kodomonokuni had poorer status than adults (P < 0.01). Comparison of the nutritional status of male and female birds of all ages revealed that, at Ueno, females had poorer status than males (P < 0.05), but there was no between-sex difference in nutritional status at Kodomonokuni (P > 0.05). In addition, comparison of nutritional status in two seasons-the breeding season (March to July) and the non-breeding season (August to February)-revealed that in both seasons both adults and juveniles had poorer status at Ueno than at Kodomonokuni (P < 0.01); the season when the birds were trapped for survey had no effect on this regional difference. Jungle crows in central Tokyo, which relied on food waste as a food resource and were densely distributed, had small physiques and poor nutritional status; malnutrition was especially apparent in growing juveniles and in females, which were disadvantaged in terms of sexual dimorphism.</p>

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