Aspects of the biology of three benthic-feeding teleosts from King’s Beach,Algoa Bay

The lengths, abundance patterns and feeding habits of three species of benthic-feeding teleosts, Lithognathus mormyrus, Lithognathus lithognathus and Umbrina capensis from King’s Beach, Algoa Bay are presented. Multiple regression analysis was used to elucidate the influence of the physical environment on the abundance of L. mormyrus. The feeding habits of these species were analysed on a quantitative basis by means of gravimetry and the frequency of occurrence of prey items.     

Sources of nutrition in intertidal sea anemones from the south-western Cape,South Africa

Respiration rates of seven species of intertidal sea anemones from the south-western Cape, South Africa were measured with and without illumination to determine whether zooxanthellae contributed to their nutritional needs. Light had no significant effect on oxygen exchange in any of the species, suggesting that all are azoox- anthellate. Diets of anemones from two sites, Wooley’s Pool in False Bay and Blouberg on the Atlantic coast some 20 km north of Cape Town, were examined by gut content analysis. Seven species occurred at Wooley’s Pool, but only one (Bunodactis reynaudi) at Blouberg. At Wooley’s Pool 39.4% of anemones contained food, while at Blouberg only 7.4% did so. A wide spectrum of prey taxa were consumed by the various anemone species, although considerable dietary overlap occurred. Pelecypods, gastropods and isopods were ingested by all the species examined. Pelecypods dominated the diet of B. reynaudi at Blouberg (91% occurrence), but were recorded in only 42% of the same species at Wooley’s Pool. The frequency of occurrence of pelecypods in the guts of the other species ranged from 9% (Anthothoe stimpsoni) to 28% (Actinia equina). Gastropods were the main prey items eaten by Anthopleura michaelseni (67% occurrence), Pseudactinia flagellifera (43%) and Pseu- dactinia varia (42%), while isopods were the most frequently occurring constituent in the diets of A. stimpsoni (62%) and Bunodosoma capensis (16%). A. equina was the only species for which insects were a regular part of the diet (26% occurrence). Platyhelminths were found only in the guts of B. capensis (11%); holothurians only in B. reynaudi at Wooley’s Pool (2%), and crinoids only in P. flagellifera (2%). Large quantities of algal material and indigestible debris were also ingested, indicating that sea anemones are non-selective feeders. Cluster analysis and multi-dimensional scaling techniques revealed four distinct feeding groups among the anemone assemblages. These are characterized as microphagous (A. stimpsoni), generalist (S. capensis and A. equina), mac- rophagous (S. reynaudi at Wooley’s Pool, A. michaelseni, P. flagellifera and P. varia) and specialist bivalve- feeder (B. reynaudi at Blouberg).     

Ontogenetic dietary shift and morphological correlates for Diplodus capensis (Teleostei: Sparidae) in southern Angola

Allometric growth patterns of functional morphological variables that reflect resource use in fish were correlated with the diet of Diplodus capensis in southern Angola. A total of 114 individuals (76–336 mm FL) were collected for stomach content analysis and a further 35 individuals (80–320 mm FL) for morphometric analysis. The major dietary components belonged to the groups Chlorophyta, Cirripedia, Rhodophyta and Bivalvia, and made up 71.7% of the diet in terms of a computed ranking index. There was a clear ontogenetic dietary shift with small fish feeding predominantly on algae and large fish on barnacles and mussels. This increasingly durophagous diet corresponded with a positive allometric growth pattern in the gape dimensions (width, height and surface area), adductor mandibulae muscle process and incisor width. Conversely, the relative gut length followed an isometric growth pattern, suggesting a decreased absorptive capacity. This isometric growth pattern is attributed to the better digestibility of the durophagous prey items when compared with algae and further corroborates a link between the morphology and an ontogenetic dietary shift observed in this species.     

Seasonal variation in the diet of Cape clawless otters (Aonyx capensis) in a marine habitat

Seasonal changes in the diet of Cape clawless otters Aonyx capensis feeding in the surf zone in False Bay, Western Cape Province, South Africa, were investigated by spraint (faecal) analysis. The most common prey species, during all seasons, was the Cape rock crab, Plagusia chabrus. The next most important prey species was the Cape rock lobster, Jasus lalandii, with the fish species Clinus superciliosus being equally important in winter. Other prey were fresh-water crabs, Potamonautes perlatus, octopus, Octopus granulatus, and 17 other species of fish, frogs and mammals. In winter and autumn the most important prey category was fish while in spring and summer, crustaceans were the most important. Diversity of prey was lowest in winter, increasing through the seasons from spring to autumn.     

The Tongue Dorsal Surface in Fish: A Comparison Among Three Farmed Species

The oral cavity of vertebrates has a very important role in many functions strictly related to the food processing. Two species, sea bass Dicentrarchus labrax and seabream Sparus aurata, are mainly involved in the aquaculture industry in the mediterranean area; moreover, the white seabream Diplodus sargus sargus was recently chosen as the best candidate for the diversification of species of commercial interest. This investigation was carried out, using the standard procedures for light and scanning electron microscopy, to analyse the morphology of the tongue dorsal surface in order to show whether relationships are present between the tongue morphology and the nutritional choices of these species. In all the three investigated species, three different areas were observed on the dorsal lingual surface: an apex, a body and a root. In the sea bass D. labrax, numerous caninelike teeth, organized in pads, were present along the dorsal surface. The presence of numerous taste buds, scattered on the tongue, was shown. In the seabream S. aurata, the apical part of the tongue is inserted in a pouch with a characteristic medial ridge on the body surface. Numerous taste buds were scattered on the whole surface. In the white seabream D. sargus sargus, a pouch partially covering the apex was clearly observed. In the pouch, filiform‐like and foliate‐like papillae can be distinguished. The results show the important role of the fish tongue in the food ingestion process, demonstrating the interaction of food processing, taste and morphological characteristics.     

Diet,dietary selectivity and density of South American grey fox,Lycalopex griseus,in Central Chile

The South American grey fox Lycalopex griseus is a canid widely distributed in southern South America; however, some aspects of its biology are still poorly known. We studied the diet and density of L. griseus in the Lago Peñuelas Biosphere Reserve, in Central Chile. The trophic niche breadth was B = 6.16 (B_sta = 0.47) and prey diversity was H′ = 2.46 (H_max′ = 3.17, J′ = 0.78). The highest proportions of prey consumed in the diet were Oryctolagus cuniculus (52.21%) and other mammals (32.78%). We compared these results with a latitudinal gradient of diet results for this species in Chile. L. griseus eats mostly mammals (>90% of total prey), consuming the rodent Phyllotis darwini and reptiles in the northern zone; Oryctolagus cuniculus, Octodon degus and Abrocoma bennetti in the central zone; Abrothrix spp. and lagomorphs in the southern zone; and Lepus capensis and Ovis aries in the austral zone. The estimated density of L. griseus in Lago Peñuelas NR was 1.3 foxes/km².     

Seasonal variations in the diet and food selection of the Algerian hedgehog Atelerix algirus

The Algerian hedgehog Atelerix algirus is an insectivorous species. However, the exact composition of its natural diet remains largely undetermined, especially in relation to seasonal variations in food availability. From March to November, we simultaneously analysed the composition of 180 hedgehog faecal samples and food availability in the Soumman Valley, Algeria to assess food selection in this species. The faeces contained 196 different prey species, of which 92% belonged to the class Insecta. The highest prey species diversity was found in the Coleoptera order (100 species recorded) and the highest species occurrence was found in Hymenoptera (65% of the prey items, mainly represented by the harvester ant Messor barbarus, a crop-ravaging species). This study shows that the Algerian hedgehog is mainly a generalist species with a diet that is strongly linked to food availability. However, seasonal variations were observed in prey selection, and a notable shift in food preference was observed during autumn. The exact nature of these changes in feeding behaviour remains to be investigated, notably in relation to changes in energy requirements of this species before hibernation, in terms of quantity and/or quality.     

Digestion rates of prey eaten by intertidal sea anemones from the south-western Cape,South Africa

Digestion rates were determined for natural prey items offered to each of seven species of sea anemones found at Wooley’s Pool in False Bay and to the single species (Bunodactis reynaudi) recorded at Biouberg on the Atlantic coast of the south-western Cape, South Africa.This was done by examining prey items removed from the coelenterons at regular intervals after feeding and assessing their degree of digestion according to a predetermined scale. There was considerable variation in the gut retention times between different anemone species offered the same prey types, with Actinia equina consistently showing the shortest gut retention times (12 h for amphipods, 15 h for pelecypods and 23 h for isopods). Of the various prey categories tested, amphipods tended to be the most rapidly digested group, while molluscs and echinoderms usually remained in the coelenteron the longest. Mean gut retention times in B. reynaudi, the only species found both in False Bay (17°C) and on the cold west coast (12°C) were markedly longer (72 vs 60 h and 43 vs 30 h for pelecypods and gastropods respectively) at the lower temperature.     

Functional responses of cougars (Puma concolor) in a multiple prey‐species system

The study of predator–prey interactions is commonly analyzed using functional responses to gain an understanding of predation patterns and the impact they have on prey populations. Despite this, little is known about predator–prey systems with multiple prey species in sites near the equator. Here we studied the functional response of cougars (Puma concolor) in relation to their main prey, armadillo (Dasypus novemcinctus), coati (Nasua narica) and white‐tailed deer (Odocoileus virginianus). Between 2004 and 2010, cougar scats were collected along 5 transects to estimate the consumption of different prey species. A relative abundance index (RAI) was calculated for each prey species and cougar using 18 camera traps. We compared Holling type I, II and III functional response models to determine patterns in prey consumption based on the relative abundance and biomass of each prey species consumed. The 3 main prey species comprised 55% (armadillo), 17% (coati) and 8% (white‐tailed deer) of the diet. Type I and II functional responses described consumption of the 2 most common prey species armadillos and coati similarly well, while a type I response best characterized consumption of white‐tailed deer. A negative correlation between the proportions of armadillo versus coati and white‐tailed deer biomass in cougar scats suggests switching to consume alternative prey, confirming high foraging plasticity of this carnivore. This work represents one of the few studies to compare functional responses across multiple prey species, combined with evidence for prey‐switching at low densities of preferred prey.     

Diet of Chinese skink,Eumeces chinensis: is prey size important?

The diet of the skink, Eumeces chinensis (Lacertilia: Scincidae), in Xiamen (Amoy), China was examined using stomach analysis during April and May, and its selection of prey size was tested by feeding trials. Insects (primarily Coleoptera, Lepidoptera, and Orthoptera), gastropods and arachnids constituted most of the E. chinensis diet, but earthworms, leeches, crustaceans and fish were also consumed. In the field, male skinks ate more prey items that were 11–20 mm in length than other size classes. When presented with a choice of different‐sized prey in the laboratory, male E. chinensis exhibited a strong preference for prey items 11–20 mm in length over other size classes. The relationship between prey size and handling time was exponential, indicating that there is an upper limit to the ability of E. chinensis to process prey. Mean energy intake for handling different‐sized prey showed that selection of midsizeclass prey items would provide male E. chinensis with the most energy‐efficient prey option. These results indicate that prey size selection in E. chinensis favors maximization of rates of energy intake, which is in agreement with optimal foraging theory.     

Note on the Taxonomy of Genetta

The recruitment patterns of six teleosts were studied at King’s Beach, Algoa Bay. February to May marked the major recruitment period for Diplodus sargus, Lithognathus mormyrus, Rhabdosargus globiceps and Trachurus capensis. The major recruitment of Sarpa salpa fry took place between August and September. Pomadasys olivaceum fry of < 5 cm total length were caught throughout the year indicating an extended breeding period. The estimated growth rates of new recruits between February and May (autumn/winter) was 0,60 cm month ^-1 for L. mormyrus, 0,75 cm month^-1 for ft globiceps and 0,40 cm month^-1 for T. capensis. The empirical growth curve derived for S. salpa indicated a growth rate of 0,75 cm month^-1. No growth estimates could be made for P. olivaceum or D. sargus.     

Food habits and trophic resource partitioning among three mormyrid fishes from man-made Lake Ayame,Ivory Coast

Feeding habits and trophic relationships among three mormyrid species (Petrocephalus bovei, Marcusenius ussheri and Marcusenius furcidens) were assessed in the man-made Lake Ayame in Ivory Coast. The index of preponderance combining the occurrence and weight percentages of the identified prey items showed that these three mormyrid species mainly feed on invertebrates, especially aquatic insects. Petrocephalus bovei mainly feeds on chaoborid larvae, whereas both Marcusenius species preferentially feed on chironomid larvae. This segregation of food items associated with the relative abundance of chironomid larvae may reduce interspecific competition between these three fish species, and may therefore allow their coexistence. Horn’s food overlap index revealed highly significant similarities in the trophic spectrum between both Marcusenius species, and for the dry as well as the rainy season.     

Systematic status of Platypleura stridula L. and Platypleura capensis L. (Hornopter,Cicadidae)

Although synonymi2ed for many decades, the Linnaean species Platypleura stridula and P. capensis are biologically distinct, differing in their host plant and habitat preferences, geographical distribution and calling songs. There are also morphological differences between the two taxa which parallel the differences in their biology. P. capensis should therefore be accorded specific rank.     

South-western extension of the known range of two freshwater shrimps,Caridina nilotica (Roux) and Macrobrachium petersi (Hilgendorf), in South Africa

Two freshwater shrimps, Caridina nilotica (Roux) and Macrobrachium petersi (Hilgendorf), were collected in the Gamtoos River in the eastern Cape, representing a southwestern range extension for both. This is the first known record of these species west of Port Elizabeth, and also the first record of an overlap of their distribution ranges with that of the Cape river shrimp, Palaemon capensis (de Man).     

Species diversity and size ranges of cephalopods in the diet of jackass penguins from Algoa Bay,South Africa

An analysis of cephalopod remains collected from jackass penguin Spheniscus demersus regurgitations and stomachs at St Croix Island, Algoa Bay, in 1976 and 1977 revealed the presence of three cephalopod species. Most common was Loligo reynaudi, with Heterotuthus sp. and Argonauta argo constituting trace items. Beak measurements were used to estimate dorsal mantle lengths and wet masses of cephalopods taken by penguins. The dominant cephalopod taken by penguins was the same species as that harvested by commercial fisheries. Despite an overlap in the size range of squid taken by penguins and trawlers, penguins tended to take smaller squid and did not take the larger squid landed by trawlers. The seasonal occurrence of squid in the penguin diet in 1976 and 1977 was the opposite of the abundance of squid in the area as reflected by trawler landings. This is explained in terms of the abundance and preference for other prey items. It is suggested that penguins take fish in preference to squid because of the relatively higher energy content and food value of fish.     

Observations on the reproductive cycles of Cellana capensis (Gmelin, 1791) and Patella concolor Krauss, 1848 (Gastropoda: Prosobranchia: Patellidae)

The reproductive periodicities of the patellid limpets Cellana capensis and Patella concolor were determined from changes in macro-and microscopic appearance of the gonads over a 14-month period. Both species appear to have protracted breeding periods with several peaks in spawning activity. Problems encountered with the application of standard sampling and analytical methods to species with such cycles are discussed.     

Problems presented by geographical variation in the African vine snakes,genus Thelotornis

Analysis of variation in 771 specimens of the genus Thelotornis A. Smith (Colubridae) confirms the absence of intergradation between the taxa kirtlandii (Hallowell) and oatesii (Gunther) in northern Angola and southern Zaire, so 7. capensis A. Smith is accepted as a full species. The western race 7. capensis oatesii shows very little variation, but the eastern populations of 7. capensis are extremely variable and it is convenient to revive the name mossambicanus (Bocage) for the populations which occur from central Mocambique northwards. T. c. oatesii hybridizes extensively with T. c. capensis and 7. c. mossambicanus in southeastern Rhodesia and adjacent Mocambique. Northern populations of 7. c. mossambicanus show features of 7. kirtlandii, but these are apparently primitive characters retained since the original partition of Thelotornis into western and eastern forms. The highlands of Kenya and northern Tanzania isolate these northern mossambicanus from the nearest kirtlandii populations in Uganda.     

Bats as the main prey of wintering long‐eared owl (Asio otus) in Beijing: Integrating biodiversity protection and urban management

The loss of biodiversity from urbanized areas is a major environmental problem challenging policy‐makers throughout the world. Solutions to this problem are urgently required in China. We carried out a case study of wintering long‐eared owls (Asio otus) and their main prey to illustrate the negative effects of urbanization combined with ineffective conservation of biodiversity in Beijing. Field monitoring of owl numbers at two roosting sites from 2004 to 2012 showed that the owl population had fallen rapidly in metropolitan Beijing. Analysis of pellet contents identified only seven individuals of two species of shrew. The majority of mammalian prey comprised four bat and seven rodent species, making up 29.3% and 29.5% of the prey items, respectively. Prey composition varied significantly among years at the two sample sites. At the urban site the consumption of bats and rodents declined gradually over time, while predation on birds increased. In contrast, at the suburban site the prey composition showed an overall decrease in the number of bats, a sharp increase and a subsequent decrease in bird prey, and the number of rodent prey fell to a low point. Rapid development of real estate and inadequate greenfield management in city parks resulted in negative effects on the bird and small mammal habitat of urban areas in Beijing. We suggest that measures to conserve biodiversity should be integrated into future urban planning to maintain China's rich biodiversity while also achieving sustainable economic development.     

Does Doramectin Use on Cattle Indirectly Affect the Endangered Burrowing Owl

Doramectin is one of several endectocide compounds widely used to treat nematode and arthropod pests affecting cattle. Insecticidal residues in dung of endectocide-treated cattle can reduce numbers of dung-breeding insects. Concerns have been raised that use of endectocides may adversely affect birds that rely on dung-breeding insects as food. However, these concerns have not been specifically addressed in previous studies. We performed two studies to collectively assess whether doramectin adversely affects burrowing owls (Athene cunicularia Molina), which are listed as “Endangered” in Canada. In the first study, insect emergence was monitored from dung of cattle treated with a recommended topical dose of doramectin. Experiments replicated in each of 3 yr showed residues reduce the number of insects developing in dung of cattle treated up to 16 wk previously. In the second study, we identified prey items from regurgitated pellets collected at 206 burrowing owl nests in southern Alberta and Saskatchewan, Canada. A total of 50 213 prey items were identified, of which 90% were invertebrates. Beetles (Coleoptera) comprised 54% of the total prey items, followed next in abundance by grasshoppers (Acrididae, 20%) and crickets (Gryllidae, 16%). Of the beetles, 1 381 specimens were identified as breeding in dung (mainly species of Aphodius, Canthon, Onthophagus). The dung beetles comprised an estimated 2.8% of the total prey items or 0.1% of total prey biomass. Results of the first study validate initial concerns that doramectin use can reduce numbers of insects breeding in dung of treated cattle. Results of the second study show reliance of burrowing owls on dung beetles is sufficiently low that use of doramectin on cattle is unlikely to appreciably affect the food supply of co-occurring burrowing owls.     

Residency and small-scale movement behaviour of three endemic sparid fishes in their shallow rocky subtidal nursery habitat,South Africa

The residency and small-scale movements of early juveniles (<175 mm fork length) of three sparid fish species were examined in the shallow subtidal zone along a 500 m stretch of rocky coastline near Schoenmakerskop (Eastern Cape Province, South Africa). A total of 12 blacktail (Diplodus capensis), 12 zebra (Diplodus hottentotus) and six white musselcracker (Sparodon durbanensis) were tagged using visible implant elastomer (VIE) tags. Underwater observations in four shallow rocky subtidal gullies and adjacent areas were made using snorkeling gear on a total of 37 days spanning 13 field trips over spring low tide periods between January and August 2006. The VIE tagging method was well suited to individually tag small juvenile fish with minimum disturbance. In general, the degree of residency of juveniles in the shallow rocky subtidal zone was species specific and dependent on the size of individuals. Juvenile zebra displayed the highest degree of residency followed by white musselcracker and blacktail, with re-sightings recorded on 53%, 40% and 10% of observation days, respectively. The high degree of residency by early juvenile sparids renders them vulnerable to localized coastal perturbations and climate change.