SYNOPSISDuring the past decade the Nile Crocodile has been greatly reduced in numbers. Scientific information on the general and breeding biology was deficient and research urgently required to ascertain the possible effects on fisheries of further drastic reduction by commercial exploitation. The results reported are based upon observations made in Uganda, Northern Rhodesia, Barotseland and Zululand during 1952, 1956 and 1957.The diurnal rhythm of activity is related to feeding and t,hermal requirements. Thermoregulation, a t about 25.5" C., is effected by habitat selection and behavioural adaptation. Information is given on terrestrial and aquatic locomotion, respiration and diving times. Evidence is presented that stomach stones, always present in the adult, are deliberately swallowed and subserve hydrostatic functions. Rate of growth is most rapid, about 265 mm. per annum, in early life : it decreases progressively to about 35 mm. per annum or less. The sexes are equal in numbers : the males grow more rapidly and attain larger size than the females. Sexual maturity is attained a t a length of about 2.9 to 3.3 metres in the male, and about 2.4 to 2-8 metres in the female, and a t an estimated age of not less than nineteen years. The breeding season, which differs with locality, coincides with the period of low water levels. Aspects of breeding behaviour in the male, including territorial defence, combat and vocalization are discussed. A pre-nuptial display in the female and inititial stages of copulation have been observed. An account is given of colonial nesting grounds, nest sites, clutch sizes and parental care by the female. Juveniles are ecologically separated from the adults.A detailed survey is made of the food and feeding habits : the diet is extremely varied ; it changes progressively with the crocodile's age ; and differs according to locality. Data relating to predatory enemies, parasites and injuries, and an account of commensal relations with three species of birds, are given. Attention is drawn to the complex web of relationships in which the species plays a part as master predator, cannibal and scavenger : its status in relation to man and to commercial fisheries is reassessed. It is concluded that C . niloticus is LL valuable member of the African fauna ; and recommendations are made for its conservation.
Summary Hornets are omnivorous scavengers: in their visits to the discarded carcases of a Palm Dove (Streptopelia senegalensis aegyptiaca) and of a Pied Kingfisher (Ceryle r. rudis) at Beni Suef, Middle Egypt, they were observed to discriminate in favour of the flesh of the dove. Selective feeding by Vespa orientalis was subsequently used as a method of assessing the relative edibility of the flesh of 38 species of birds in terms of hornet preference. During the period 1941–1944, 141 hornet experiments were carried out in Egypt and the Lebanon: in each experiment the insects were presented with a choice as between the flesh of two species of birds, or (in control tests) of the same species. The two food elements offered in each experiment were approximately similar in bulk and anatomical content, but the quantity and quality were varied from one experiment to another throughout the series. The number of insects feeding at each carcase was counted at regular intervals of (usually) five minutes, until one food element had been exhausted, preference for one bird of the pair being established by a differential rate of attack, based on the total number of hornets counted at each food element. Experimental data are tabulated to show: (a) the total number of hornets counted at each test; (b) the ratio of attack at the two food elements; (c) standard error;(d) observed deviation. The consistency of hornet discrimination and reliability of the experimental method was checked by linking and overlapping experiments (between pairs of species more or less widely separated in the edibility series);and by repetition and control experiments (between similar pairs, or the same species). In general, the experimental data show the hornets to be highly sensitive to differences in the relative palatability of the birds offered. Thirty‐eight species of birds tested include: members of several Passerine families—Oriolidae, Fringillidae, Ploceidae, Alaudidae, Motacillidae, Paridae, Laniidae, Pycnonotidae, Sylviidae, Turdidae and Hirundinidae; and of other orders— Coraciiformes, Piciformes, Strigiformes, Ciconiiformes and Columbiformes. Arranged in order of acceptability, they fall into the following groups:— Palatable: Wryneck (Jynx t. torquilla), Crested Lark (Galerida cristata magna, G. c. maculata), White‐vented Bulbul (Pycnonotus barbatus arsinöe), Buff‐backed Heron (Ardeola i. ibis), Greenfinch (Chloris chloris chlorotica), Little Green Bee‐eater (Merops orientalis cleopatra), Palm Dove (Streptopelia senegalensis aegyptiaca), House Sparrow (Passer domesticus niloticus, P. d. biblicus), Spanish Sparrow (Passer h. hispaniolensis), Pied Chat (Oenanthe pleschanka), Spotted Flycatcher (Muscicapa s. striata), Blue‐headed Wagtail (Motacilla f. flava), Lesser Whitethroat (Sylvia c. curruca). Intermediate: Little Owl (Athene noctua lilith), Cretzschmar's Bunting (Emberiza caesia), Goldfinch (Carduelis c. niediecki), Rufous Warbler (Erythropygia g. galactote.s), White Stork (Ciconia c. ciconia), Garden Warbler (Sylvia borin), Willow Warble...
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