scholarly journals Passive Prey Discrimination in Surface Predatory Behaviour of Bait-Attracted White Sharks from Gansbaai, South Africa

Animals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2583
Author(s):  
Primo Micarelli ◽  
Federico Chieppa ◽  
Antonio Pacifico ◽  
Enrico Rabboni ◽  
Francesca Romana Reinero
Keyword(s):  
South Africa ◽  
Food Choice ◽  
Predatory Behaviour ◽  
Dietary Shift ◽  
Total Length ◽  
Prey Discrimination ◽  
Training Area

Between the years 2008 and 2013, six annual research expeditions were carried out at Dyer Island (Gansbaai, South Africa) to study the surface behaviour of white sharks in the presence of two passive prey: tuna bait and a seal-shaped decoy. Sightings were performed from a commercial cage-diving boat over 247 h; 250 different white sharks, with a mean total length (TL) of 308 cm, were observed. Of these, 166 performed at least one or more interactions, for a total of 240 interactions with bait and the seal-shaped decoy. In Gansbaai, there is a population of transient white sharks consisting mainly of immature specimens throughout the year. Both mature and immature sharks preferred to prey on the seal-shaped decoy, probably due to the dietary shift that occurs in white sharks whose TL varies between 200 cm and 340 cm. As it is widely confirmed that white sharks change their diet from a predominantly piscivorous juvenile diet to a mature marine mammalian diet, it is possible that Gansbaai may be a hunting training area and that sharks show a discriminate food choice, a strategy that was adopted by the majority of specimens thanks to their ability to visualize energetically richer prey, after having been attracted by the odorous source represented by the tuna bait.

Larval sand lance (Ammodytes sp.) in the diet of small juvenile wolffish (Anarhichas spp.): predatory interactions in frontal water masses off western Greenland

2002 ◽  
Vol 59 (11) ◽  
pp. 1759-1767 ◽  
Author(s):  
Peter Munk
Keyword(s):  
Fish Larvae ◽  
Stomach Contents ◽  
Prey Type ◽  
Ontogenetic Changes ◽  
Sand Lance ◽  
Larval Size ◽  
Predatory Behaviour ◽  
Dietary Shift ◽  
Abundance Estimates ◽  
Anarhichas Lupus

The predatory behaviour of two species of juvenile wolffish (Anarhichas lupus and Anarhichas minor) was studied during a field campaign across a frontal area off western Greenland. The study focused on ontogenetic changes in prey-type and -size preference of the wolffish and their predatory impact on a cohabiting population of larval sand lance (Ammodytes sp.). Sampling took place along a cross-shelf transect at latitude 66°20' N, and the analysis is based on stomach contents of assembled wolffish (2–5 cm in length) and abundance estimates of plankton and fish. An ontogenetic change in wolffish prey preference was evident as a dietary shift from copepods and smaller amphipods to larger amphipods and fish larvae. The inclusion of fish larvae in the wolffish diet led to a marked increase in prey biomass, and fish larvae constituted up to 77% of diet biomass in the largest juveniles caught. Wolffish selectively targeted the smaller-sized part of the larval sand lance population; hence, larval vulnerability increased with decreasing size. Comparison between estimated predation rates and abundances of predator and prey indicated larval predation mortalities of up to 5% per day, with mortality peaking in the vicinity of a hydrographic front. Hence, findings suggest substantial predation pressure on larvae, primarily related to larval size and distribution.

scholarly journals Preliminary observations of tag shedding, tag reporting, tag wounds, and tag biofouling for raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa

2006 ◽  
Vol 63 (9) ◽  
pp. 1640-1648 ◽  
Author(s):  
M.L. Dicken ◽  
A.J. Booth ◽  
M.J. Smale
Keyword(s):  
South Africa ◽  
East Coast ◽  
Telephone Survey ◽  
Total Length ◽  
Significant Difference ◽  
Juvenile Sharks ◽  
Carcharias Taurus ◽  
Tag Shedding

Abstract A double-tagging experiment and integrated on-site questionnaire and telephone survey were used to investigate aspects of tag shedding, tag reporting, tag wounds, and tag biofouling for the raggedtooth shark (Carcharias taurus), tagged off the east coast of South Africa. Between 2002 and 2004, 84 juvenile (<1.8 m total length, TL), and 24 adult (>1.8 m TL) C. taurus were double-tagged. Of these, 11 juvenile and six adult double-tagged sharks were recaptured. Significantly, more tags were shed from adult than from juvenile sharks, and there was also a significant difference between the number of anterior and posterior tags shed. Rates of tag reporting were estimated from a survey of 477 randomly selected shore-anglers, and they varied both temporally and spatially from 27% to 100%. In all, 93 tag recaptures were reported in the survey, most (75.3%) with some biofouling. Tag-inflicted damage was reported in 35.5% of recaptured sharks, and the incidence of tag-inflicted damage was greater for disk (77.8%) than for dart tags (25.3%).

scholarly journals Movement and Home Range of Nile Crocodiles in Ndumo Game Reserve, South Africa

Koedoe ◽  
2015 ◽  
Vol 57 (1) ◽  
Author(s):  
Peter M. Calverley ◽  
Colleen T. Downs
Keyword(s):  
South Africa ◽  
Home Range ◽  
Satellite Telemetry ◽  
Movement Patterns ◽  
Breeding Site ◽  
Water Levels ◽  
Home Ranges ◽  
Total Length ◽  
Game Reserve ◽  
Nile Crocodile

The study of movement patterns and home range is fundamental in understanding the spatial requirements of animals and is important in generating information for the conservation and management of threatened species. Ndumo Game Reserve, in north-eastern KwaZulu-Natal, bordering Mozambique, has the third largest Nile crocodile (Crocodylus niloticus) population in South Africa. Movement patterns of 50 Nile crocodiles with a total length of between 202 cm and 472 cm were followed over a period of 18 months, using mark-resight, radio and satellite telemetry. The duration of radio transmitter attachment (131 ± 11.4 days) was significantly and negatively related to total length and reproductive status. Satellite transmitters failed after an average of 15 ± 12.5 days. Home range was calculated for individuals with 10 or more radio locations, spanning a period of at least 6 months. There was a significant relationship between home range size and total length, with sub-adults (1.5 m – 2.5 m) occupying smaller, more localised home ranges than adults (> 2.5 m). The largest home ranges were for adults (> 2.5 m). Home ranges overlapped extensively, suggesting that territoriality, if present, does not result in spatially discrete home ranges of Nile crocodiles in Ndumo Game Reserve during the dry season. Larger crocodiles moved farther and more frequently than smaller crocodiles. The reserve acts as a winter refuge and spring breeding site for an estimated 846 crocodiles, which also inhabit the Rio Maputo during the summer months. Nile crocodile movement out of the reserve and into the Rio Maputo starts in November and crocodiles return to the reserve as water levels in the floodplain recede in May.Conservation implications: Movement patterns of Nile crocodiles show the important role the reserve plays in the conservation of Nile crocodile populations within the greater Ndumo Game Reserve–Rio Maputo area.

predatory behaviour of white sharks (carcharodon carcharias) at seal island, south africa

2005 ◽  
Vol 85 (5) ◽  
pp. 1121-1135 ◽  
Author(s):  
r. aidan martin ◽  
neil hammerschlag ◽  
ralph s. collier ◽  
chris fallows
Keyword(s):  
South Africa ◽  
Success Rate ◽  
White Shark ◽  
Predatory Fish ◽  
Success Rates ◽  
Carcharodon Carcharias ◽  
Predatory Behaviour ◽  
Video Footage ◽  
Anterior Teeth ◽  
Fur Seals

between 1997 and 2003, there were 2088 natural predations by white sharks (carcharodon carcharias) on cape fur seals (arctocephalus pusillus pusillus) and 121 strikes on towed seal-shaped decoys were documented from observation vessels at seal island, south africa. white sharks at seal island appear to selectively target lone, incoming young of the year cape fur seals at or near the surface. most attacks lasted <1 min and consisted of a single breach, with predatory success rate decreasing rapidly with increasing duration and number of subsequent breaches. a white shark predatory ethogram, composed of four phases and 20 behavioural units, is presented, including four varieties of initial strike and 11 subsequent behaviour units not previously defined in the literature. behaviour units scored from 210 predatory attacks revealed that, for both successful and unsuccessful attacks, polaris breach was the most commonly employed initial strike, while surface lunge was the most frequent second event, closely followed by lateral snap. examination of video footage, still images, and tooth impressions in decoys indicated that white sharks at seal island bite prey obliquely using their anterolateral teeth via a sudden lateral snap of the jaws and not perpendicularly with their anterior teeth, as previously supposed. analysis of white shark upper tooth morphology and spacing suggest the reversed intermediate teeth of white sharks occur at the strongest part of the jaw and produce the largest wound. white shark predatory success at seal island is greatest (55%) within one hour of sunrise and decreases rapidly with increasing ambient light; the sharks cease active predation on seals when success rate drops to ±40%; this is the first evidence of cessation of foraging at unproductive times by any predatory fish. at seal island, white shark predatory success is significantly lower at locations where frequency of predation is highest, suggesting that white sharks may launch suboptimal strikes in areas of greatest intraspecific competition; this is the first evidence of social influence on predation in any elasmobranch. idiosyncratic predatory behaviours and elevated success rates of known individual white sharks at seal island suggest some degree of trial-and-error learning. a hypothetical decision tree is proposed that models predatory behaviour of white sharks attacking cape fur seals at the surface.

scholarly journals A New Species of Afrotropical Ants in the GenusBothroponera(Hymenoptera: Formicidae: Ponerinae)

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Abdulmeneem M. A. Joma ◽  
William P. Mackay
Keyword(s):  
South Africa ◽  
New Species ◽  
The Other ◽  
Eastern Cape Province ◽  
Eastern Cape ◽  
Complex Species ◽  
Total Length ◽  
A New Species

We describe a new species of AfrotropicalBothroponerafrom Whittlesea City, Eastern Cape Province, South Africa. This species is unique among the AfricanBothroponeraas it is the only species with a horizontal propodeal spiracle. It is also the largest species of AfricanBothroponera(total length 14.80–15.65). The clypeus lacks a medial longitudinal carina, the head is subquadrate, the sculpture is mostly foveolate, and the second gastral segment nearly lacks sculpturing. We compare the new species to the similarB. cavernosaandB. cavernosavar.montivaga. We also compare the new species to all of the other 10 taxa that belong to thecavernosacomplex. A key to thecavernosacomplex species of the AfrotropicalBothroponerais provided along with diagnosis, comparison, distribution, habitat, biology, and etymology for the new species.

Aspects of the biology and life history of largespot pompano, Trachinotus botla, in South Africa

2015 ◽  
Vol 66 (3) ◽  
pp. 247 ◽  
Author(s):  
D. Parker ◽  
A. J. Booth
Keyword(s):  
South Africa ◽  
Surf Zone ◽  
Fork Length ◽  
Small Fish ◽  
Dietary Shift ◽  
Opportunistic Predator ◽  
History Of ◽  
Spawning Behaviour ◽  
Generalist Diet ◽  
Terrestrial Insects

Trachinotus botla is an important recreational surf zone-dependent fish species distributed in the Indo-west Pacific from South Africa to Australia. In South Africa it is restricted to the northern KwaZulu-Natal coast. Biological investigations revealed that it is a fast growing species that attains a maximum age of ~7 years. Males and females sexually matured in their third year. It has a protracted summer spawning season with evidence of serial spawning behaviour. T. botla is an opportunistic predator with a generalist diet, with fish feeding on a wide variety of prey items particularly those that are temporally ‘superabundant’. Small fish fed predominantly on copepods and terrestrial insects, whereas larger fish consumed bivalves and crabs. Teleosts, primarily engraulids, were important components to the diet of fish of all sizes. An ontogenetic dietary shift was observed just after sexual maturity (~300-mm fork length) that is possibly linked to a change in habitat preference with larger fish foraging on deeper reefs.

scholarly journals Effects of sensory mode in prey discrimination and predatory behaviour of rock lizards

2020 ◽  
Vol 42 (1) ◽  
pp. 125-132
Author(s):  
Pablo Recio ◽  
Gonzalo Rodríguez-Ruiz ◽  
José Martín
Keyword(s):  
Visual Cues ◽  
Prey Species ◽  
Foraging Ecology ◽  
Sensory System ◽  
Predatory Behaviour ◽  
Sensory Mode ◽  
Rock Lizard ◽  
Prey Discrimination ◽  
Tongue Flicks ◽  
Number Of Individuals

Abstract An essential part of foraging ecology is to understand the processes of detection, recognition and discrimination of prey, as well as the sensorial modalities involved. Often, predators do not rely on a single sensory system but on multiple interacting senses. Specifically, lizards mainly use vision and vomerolfaction for prey pursuit. Here, we used an experimental approach to study how the Carpetan rock lizard, Iberolacerta cyreni, responds to different types of stimuli (chemical, visual, or both combined) from two prey species. The number of individuals approaching the prey and the number of attacks differed between treatments, however, we did not find differences in latency time, number of individuals attacking the prey or number of tongue flicks. Our results suggested that visual cues combined with chemical stimuli enhanced detection of both prey species and that prey discrimination occurred posteriorly and independently of using any or both types of stimuli.

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