Journal of Fish Biology (2014) 84, 263–266 doi:10.1111/jfb.12278, available online at wileyonlinelibrary.com
First observation of African tigerfish Hydrocynus vittatus predating on barn swallows Hirundo rustica in flight G. C. O’Brien, F. Jacobs, S. W. Evans and N. J. Smit* Water Research Group (Ecology), Unit of Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa (Received 31 May 2013, Accepted 14 October 2013) A population of African tigerfish Hydrocynus vittatus from the Schroda Dam, actively prey on barn swallows Hirundo rustica in flight. This behaviour was discovered during a radio telemetry study and documented using a motion picture video camera. These results show that an avivorous diet is a part of the feeding biology of H. vittatus, and may occur in other populations. © 2013 The Fisheries Society of the British Isles
Key words: avivorous behaviour; feeding behaviour; freshwater fish; predation; South Africa.
Aquatic animals are known to prey on birds from their aquatic environments (Glegg, 1945; Lovvorn et al., 2010). Many marine sharks and other predatory fishes are known to exhibit this avivorous behaviour (Glegg, 1945, 1947; Davenport, 1979; French, 1981). Although the predation of birds by freshwater fishes has rarely been documented, some bass species (Micropterus spp.), eels (Anguilla spp.), piranhas Serrasalmus piraya (Cuvier 1819) and pike Esox lucius L. 1758 have been shown to prey on birds occasionally (Glegg, 1945; Craig, 1996; Hodgson & Hansen, 2005). This behaviour of fishes involves preying on swimming, floating or stationary birds on land close to the edge of the water. There are also limited accounts of some freshwater fishes lunging out of the water to catch small stationary birds (Marshall, 2011). This includes largemouth bass Micropterus salmoides (Lac´ep`ede 1802) individuals taking a reed warbler Acrocephalus gracilirostris from a reed and a masked weaver Ploceus velatus from c. 15 cm above the surface. In addition, there have been speculations that members of one genus of African freshwater fish, Hydrocynus spp. known as the African tigerfish, have the ability to lunge out of the water and prey on birds in flight (Glegg, 1945; Oatley, 1960; Pyper, 2007). Oatley (1960) reported the possible predation of barn swallows Hirundo rustica at Ndumu Game Reserve in South Africa by Hydrocynus vittatus Castelnau 1861. Although he never saw it, Oatley (1960) attributed the disappearance of H. rustica individuals flying over the surface of the lake to the presence of a large population of H. vittatus in the lake. Similarly, Glegg (1945) documents a verbal account of A. L. Butler who *Author to whom correspondence should be addressed. Tel.: +272992128; email: [email protected]
263 © 2013 The Fisheries Society of the British Isles
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observed red-throated bee-eaters Merops bulocki disappearing (two birds in half an hour) while skimming over the water surface of isolated pools in the Rahad and Diner Rivers. This was attributed to large fish occurring in the pools which Butler thought might possibly be a Hydrocynus sp. Pyper (2007) also provided an anecdotal account of what appears to be H. vittatus, preying on a swallow in flight in the Komati River, South Africa. The aim of this study was therefore to document the in-flight avivorous behaviour of a population of H. vittatus, previously observed in Schroda Dam, a man-made lake in Limpopo Province, South Africa (F. Jacobs, pers. obs.). The Schroda Dam, a small 4·1 × 106 m3 off-channel storage lake, was constructed in 1993 in the Limpopo River catchment in the Mapungubwe National Park, South Africa (22◦ 11 32·54 S; 29◦ 25 59·93 E) (P. S. O. Fouch´e, unpubl. data). A population of locally threatened H. vittatus was established in Schroda Dam in 2003 (P. S. O. Fouch´e, unpubl. data). Recently, O’Brien et al. (2012) characterized the feeding behaviour of the H. vittatus population in Schroda Dam and found that they demonstrated routine crepuscular, piscivorous feeding patterns. Active roaming movements in deep open water adjacent to well-vegetated areas, or areas with structure in the limnetic zone along the periphery of Schroda, were associated with this feeding behaviour (O’Brien et al., 2012). During the day (0800 to 1600 hours) H. vittatus characteristically occupied deep sheltered areas where their activity decreased (O’Brien et al., 2012). During a summer (February 2011) survey at least five radiotagged H. vittatus individuals displayed daily uncharacteristic increases in midmorning activity (0800 to 1200 hours). This occurred in an open-water area of Schroda Dam that was not associated with shelter and traditional feeding areas. Observations revealed that the timing and location of the unique behaviour was associated with low-flying migrant H. rustica that were feeding or drinking while in flight above the lake. Although none of the five tagged individuals were observed attempting to prey on the H. rustica individuals, numerous successful (c. 25% of attempts) and unsuccessful aerial attacks by other (untagged) H. vittatus individuals were observed. Some of these attacks were documented using a motion picture video camera (Sony DP170 Camcorder; www.sony.com) (Video S1, Supporting information). During the 15 day survey as many as 20 successful attempts by H. vittatus individuals were observed on a daily basis. Two predation strategies were displayed by H. vittatus. These included surface or sub-surface pursuits of H. rustica (Video S1, Supporting information), followed by aerial strikes, and direct aerial strikes initiated from deeper water (>0·5 m) (Videos S2 and S3, Supporting information). The surfacepursuit strategy was less successful (approximately one of seven attempts was successful) compared to direct aerial strikes initiated from deeper areas (approximately one of three attempts was successful). The surface-pursuit strategy appeared to be adopted by H. vittatus [Fig. 1(b)] that were unable to compensate for the image shift of the low-flying H. rustica [Fig. 1(a)] caused by the refraction of light on the surface of the water (Fig. 1, angle θ). The direct aerial strikes were adopted by those H. vittatus [Fig. 1(c)] that appeared to be able to compensate for the image shift and successfully prey on low-flying H. rustica [Fig. 1(a)]. Many other fishes, including the welldocumented archer fishes (Toxotidae) and South American arowana Osteoglossum spp., compensate for optical distortions caused by refraction of light and effectively target moving terrestrial animals (Timmermans, 2001; Lowry et al., 2005; Schuster et al., 2006). Similarly, the direct aerial strike approach adopted by the Schroda Dam
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
H Y D R O C Y N U S V I T TA T U S C AT C H I N G H I R U N D O R U S T I C A
265
(a)
θ
θ
(b)
(c)
Fig. 1. Avivorous behavioural strategies adopted by Hydrocynus vittatus in the Schroda Dam man-made lake. (a) Flight path of the prey Hirundo rustica, (b) surface pursuit strategy of H. vittatus to overcome surface image shift due to light refraction (angle θ ) and (c) direct aerial strikes by adult H. vittatus that compensate for the image shift (not drawn to scale).
H. vittatus suggests that they too can compensate for the image shift despite the fact that this ability was not a prerequisite for catching H. rustica, as demonstrated by the success of the surface-pursuit strategy. Being able to compensate for the image shift, however, appears to be more effective and results in a higher success rate. During the 15 day survey as many as 300 H. rustica individuals were preyed upon by the local H. vittatus population, indicating that this feeding behaviour is not occasional as suggested by Glegg (1945) or Ballard & Ainley (2005). This behaviour may have been adopted out of necessity due to food availability limitations. O’Brien et al. (2012) showed that the Schroda Dam H. vittatus spend considerably more time foraging (up to three times more), possibly due to paucity of available food in the lake, when compared with other local populations. Ecosystem coupling in the form of nutrient flow from the terrestrial ecosystem to the lake aquatic ecosystem through predation [similar to Mehner et al. (2005)], may be a major contributor to the survival capability of this locally protected H. vittatus population. In addition, this feeding behaviour may increase the risk of the H. vittatus themselves being preyed upon by avian predators such as the African fish eagle Haliaeetus vocifer which are common in the area. The importance of this seasonal allochthonous nutrient source to Schroda Dam and its H. vittatus population should be further explored. The outcomes of this study confirm that H. vittatus actively prey on low-flying H. rustica during summer. In addition, these results show that an avivorous diet is part of the feeding biology of H. vittatus, and that in-flight avivorous behaviour in other Hydrocynus spp. is plausible. As far as is known, this is the first confirmed record of a freshwater fish preying on birds in flight. The conservation implications associated with this predation pressure on H. rustica by the Schroda Dam H. vittatus and possible cumulative depredations on Hirundidae by tigerfishes over Africa’s wetlands should be further investigated. The 8th European Development Fund (EDF) Programme is acknowledged for funding the Botswana Economic Diversification of the Mining Sector (EDMS)
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
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Project, J. Bulfin (Galway-Mayo Institute of Technology, Ireland) for field assistance and The Diamond Route, and the Venetia Limpopo Nature Reserve for logistical support during fieldwork. Supporting Information Supporting Information may be found in the online version of this paper: Video S1. Surface and sub-surface pursuits of Hirundo rustica by Hydrocynus vittatus; Unsuccessful and successful aerial strike of Hydrocynus vittatus on Hirundo rustica from deep water.
References Ballard, G. & Ainley, D. G. (2005). Killer whale harassment of Ad´elie penguins at Ross Island. Antarctic Science 17, 385–386. Craig, J. F. (Ed) (1996). Pike: Biology and Exploitation. London: Chapman & Hall. Davenport, L. J. (1979). Shag swallowed by monkfish. Bulletin of British Ornithology Club 72, 77–78. French, T. W. (1981). Fish attack on black guillemot Cepphus grylle and common eider Somateria mollissima in Maine USA. Wilson Library Bulletin 93, 279–280. Glegg, W. E. (1945). Fishes and other aquatic animals preying on birds. Ibis 87, 422–433. Glegg, W. E. (1947). Fishes and other aquatic animals preying on birds: additional matter. Ibis 89, 433–435. Hodgson, J. R. & Hansen, E. M. (2005). Terrestrial prey items in the diet of largemouth bass, Micropterus salmoides, in a small north temperate lake. Journal of Freshwater Ecology 20, 793–794. Lovvorn, J. R., Wilson, J. J., McKay, D., Bump, J. K., Cooper, L. W. & Grebmeier, J. M. (2010). Walruses attack spectacled eiders wintering in pack ice of the Bering Sea. Arctic 63, 53–56. Lowry, D., Wintzer, A. P., Matott, M. P., Whitenack, L. B., Huber, D. R., Dean, M. & Motta, P. J. (2005). Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum. Environmental Biology of Fishes 73, 453–462. Marshall, B. (2011). The Fishes of Zimbabwe and their Biology. Grahamstown: South African Institute for Aquatic Biodiversity. Mehner, T., Ihlau, J., D¨orner, H. & H¨olker, F. (2005). Can feeding of fish on terrestrial insects subsidize the nutrient pool of lakes? Limnology and Oceanography 50, 2022–2031. Oatley, T. B. (1960). Miscellaneous notes of natural history interest. 5. Swallows taken by tigerfish. Lammergeyer 1, 37–38. O’Brien, G. C., Bulfin, J. B., Husted, A. & Smit, N. J. (2012). A comparative behavioural assessment of an established and new tigerfish (Hydrocynus vittatus) population in two artificial impoundments in the Limpopo catchment, Southern Africa. African Journal of Aquatic Sciences 37, 253–263. Pyper, C. (2007). Stillwater trout, tigerfish, Clanwilliam yellows, Garrick, queenfish. In Favoured Flies & Select Techniques of the Experts, Vol. 3 (Meintjes, M. & Pedder, M., eds), pp. 79–86. Johannesburg: Federation of Southern African Flyfishers. Schuster, S., W¨ohl, S., Griebsch, M. & Klostermeier, I. (2006). Animal cognition: how archer fish learn to down rapidly moving targets. Current Biology 16, 378–383. Timmermans, P. J. A. (2001). Prey catching in the archer fish: angles and probability of hitting an aerial target. Behavioural Processes 55, 93–105.
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
First observation of African tigerfish Hydrocynus vittatus predating on barn swallows Hirundo rustica in flight G. C. O’Brien, F. Jacobs, S. W. Evans and N. J. Smit* Water Research Group (Ecology), Unit of Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa (Received 31 May 2013, Accepted 14 October 2013) A population of African tigerfish Hydrocynus vittatus from the Schroda Dam, actively prey on barn swallows Hirundo rustica in flight. This behaviour was discovered during a radio telemetry study and documented using a motion picture video camera. These results show that an avivorous diet is a part of the feeding biology of H. vittatus, and may occur in other populations. © 2013 The Fisheries Society of the British Isles
Key words: avivorous behaviour; feeding behaviour; freshwater fish; predation; South Africa.
Aquatic animals are known to prey on birds from their aquatic environments (Glegg, 1945; Lovvorn et al., 2010). Many marine sharks and other predatory fishes are known to exhibit this avivorous behaviour (Glegg, 1945, 1947; Davenport, 1979; French, 1981). Although the predation of birds by freshwater fishes has rarely been documented, some bass species (Micropterus spp.), eels (Anguilla spp.), piranhas Serrasalmus piraya (Cuvier 1819) and pike Esox lucius L. 1758 have been shown to prey on birds occasionally (Glegg, 1945; Craig, 1996; Hodgson & Hansen, 2005). This behaviour of fishes involves preying on swimming, floating or stationary birds on land close to the edge of the water. There are also limited accounts of some freshwater fishes lunging out of the water to catch small stationary birds (Marshall, 2011). This includes largemouth bass Micropterus salmoides (Lac´ep`ede 1802) individuals taking a reed warbler Acrocephalus gracilirostris from a reed and a masked weaver Ploceus velatus from c. 15 cm above the surface. In addition, there have been speculations that members of one genus of African freshwater fish, Hydrocynus spp. known as the African tigerfish, have the ability to lunge out of the water and prey on birds in flight (Glegg, 1945; Oatley, 1960; Pyper, 2007). Oatley (1960) reported the possible predation of barn swallows Hirundo rustica at Ndumu Game Reserve in South Africa by Hydrocynus vittatus Castelnau 1861. Although he never saw it, Oatley (1960) attributed the disappearance of H. rustica individuals flying over the surface of the lake to the presence of a large population of H. vittatus in the lake. Similarly, Glegg (1945) documents a verbal account of A. L. Butler who *Author to whom correspondence should be addressed. Tel.: +272992128; email: [email protected]
263 © 2013 The Fisheries Society of the British Isles
264
G. C. O’BRIEN ET AL.
observed red-throated bee-eaters Merops bulocki disappearing (two birds in half an hour) while skimming over the water surface of isolated pools in the Rahad and Diner Rivers. This was attributed to large fish occurring in the pools which Butler thought might possibly be a Hydrocynus sp. Pyper (2007) also provided an anecdotal account of what appears to be H. vittatus, preying on a swallow in flight in the Komati River, South Africa. The aim of this study was therefore to document the in-flight avivorous behaviour of a population of H. vittatus, previously observed in Schroda Dam, a man-made lake in Limpopo Province, South Africa (F. Jacobs, pers. obs.). The Schroda Dam, a small 4·1 × 106 m3 off-channel storage lake, was constructed in 1993 in the Limpopo River catchment in the Mapungubwe National Park, South Africa (22◦ 11 32·54 S; 29◦ 25 59·93 E) (P. S. O. Fouch´e, unpubl. data). A population of locally threatened H. vittatus was established in Schroda Dam in 2003 (P. S. O. Fouch´e, unpubl. data). Recently, O’Brien et al. (2012) characterized the feeding behaviour of the H. vittatus population in Schroda Dam and found that they demonstrated routine crepuscular, piscivorous feeding patterns. Active roaming movements in deep open water adjacent to well-vegetated areas, or areas with structure in the limnetic zone along the periphery of Schroda, were associated with this feeding behaviour (O’Brien et al., 2012). During the day (0800 to 1600 hours) H. vittatus characteristically occupied deep sheltered areas where their activity decreased (O’Brien et al., 2012). During a summer (February 2011) survey at least five radiotagged H. vittatus individuals displayed daily uncharacteristic increases in midmorning activity (0800 to 1200 hours). This occurred in an open-water area of Schroda Dam that was not associated with shelter and traditional feeding areas. Observations revealed that the timing and location of the unique behaviour was associated with low-flying migrant H. rustica that were feeding or drinking while in flight above the lake. Although none of the five tagged individuals were observed attempting to prey on the H. rustica individuals, numerous successful (c. 25% of attempts) and unsuccessful aerial attacks by other (untagged) H. vittatus individuals were observed. Some of these attacks were documented using a motion picture video camera (Sony DP170 Camcorder; www.sony.com) (Video S1, Supporting information). During the 15 day survey as many as 20 successful attempts by H. vittatus individuals were observed on a daily basis. Two predation strategies were displayed by H. vittatus. These included surface or sub-surface pursuits of H. rustica (Video S1, Supporting information), followed by aerial strikes, and direct aerial strikes initiated from deeper water (>0·5 m) (Videos S2 and S3, Supporting information). The surfacepursuit strategy was less successful (approximately one of seven attempts was successful) compared to direct aerial strikes initiated from deeper areas (approximately one of three attempts was successful). The surface-pursuit strategy appeared to be adopted by H. vittatus [Fig. 1(b)] that were unable to compensate for the image shift of the low-flying H. rustica [Fig. 1(a)] caused by the refraction of light on the surface of the water (Fig. 1, angle θ). The direct aerial strikes were adopted by those H. vittatus [Fig. 1(c)] that appeared to be able to compensate for the image shift and successfully prey on low-flying H. rustica [Fig. 1(a)]. Many other fishes, including the welldocumented archer fishes (Toxotidae) and South American arowana Osteoglossum spp., compensate for optical distortions caused by refraction of light and effectively target moving terrestrial animals (Timmermans, 2001; Lowry et al., 2005; Schuster et al., 2006). Similarly, the direct aerial strike approach adopted by the Schroda Dam
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
H Y D R O C Y N U S V I T TA T U S C AT C H I N G H I R U N D O R U S T I C A
265
(a)
θ
θ
(b)
(c)
Fig. 1. Avivorous behavioural strategies adopted by Hydrocynus vittatus in the Schroda Dam man-made lake. (a) Flight path of the prey Hirundo rustica, (b) surface pursuit strategy of H. vittatus to overcome surface image shift due to light refraction (angle θ ) and (c) direct aerial strikes by adult H. vittatus that compensate for the image shift (not drawn to scale).
H. vittatus suggests that they too can compensate for the image shift despite the fact that this ability was not a prerequisite for catching H. rustica, as demonstrated by the success of the surface-pursuit strategy. Being able to compensate for the image shift, however, appears to be more effective and results in a higher success rate. During the 15 day survey as many as 300 H. rustica individuals were preyed upon by the local H. vittatus population, indicating that this feeding behaviour is not occasional as suggested by Glegg (1945) or Ballard & Ainley (2005). This behaviour may have been adopted out of necessity due to food availability limitations. O’Brien et al. (2012) showed that the Schroda Dam H. vittatus spend considerably more time foraging (up to three times more), possibly due to paucity of available food in the lake, when compared with other local populations. Ecosystem coupling in the form of nutrient flow from the terrestrial ecosystem to the lake aquatic ecosystem through predation [similar to Mehner et al. (2005)], may be a major contributor to the survival capability of this locally protected H. vittatus population. In addition, this feeding behaviour may increase the risk of the H. vittatus themselves being preyed upon by avian predators such as the African fish eagle Haliaeetus vocifer which are common in the area. The importance of this seasonal allochthonous nutrient source to Schroda Dam and its H. vittatus population should be further explored. The outcomes of this study confirm that H. vittatus actively prey on low-flying H. rustica during summer. In addition, these results show that an avivorous diet is part of the feeding biology of H. vittatus, and that in-flight avivorous behaviour in other Hydrocynus spp. is plausible. As far as is known, this is the first confirmed record of a freshwater fish preying on birds in flight. The conservation implications associated with this predation pressure on H. rustica by the Schroda Dam H. vittatus and possible cumulative depredations on Hirundidae by tigerfishes over Africa’s wetlands should be further investigated. The 8th European Development Fund (EDF) Programme is acknowledged for funding the Botswana Economic Diversification of the Mining Sector (EDMS)
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
266
G. C. O’BRIEN ET AL.
Project, J. Bulfin (Galway-Mayo Institute of Technology, Ireland) for field assistance and The Diamond Route, and the Venetia Limpopo Nature Reserve for logistical support during fieldwork. Supporting Information Supporting Information may be found in the online version of this paper: Video S1. Surface and sub-surface pursuits of Hirundo rustica by Hydrocynus vittatus; Unsuccessful and successful aerial strike of Hydrocynus vittatus on Hirundo rustica from deep water.
References Ballard, G. & Ainley, D. G. (2005). Killer whale harassment of Ad´elie penguins at Ross Island. Antarctic Science 17, 385–386. Craig, J. F. (Ed) (1996). Pike: Biology and Exploitation. London: Chapman & Hall. Davenport, L. J. (1979). Shag swallowed by monkfish. Bulletin of British Ornithology Club 72, 77–78. French, T. W. (1981). Fish attack on black guillemot Cepphus grylle and common eider Somateria mollissima in Maine USA. Wilson Library Bulletin 93, 279–280. Glegg, W. E. (1945). Fishes and other aquatic animals preying on birds. Ibis 87, 422–433. Glegg, W. E. (1947). Fishes and other aquatic animals preying on birds: additional matter. Ibis 89, 433–435. Hodgson, J. R. & Hansen, E. M. (2005). Terrestrial prey items in the diet of largemouth bass, Micropterus salmoides, in a small north temperate lake. Journal of Freshwater Ecology 20, 793–794. Lovvorn, J. R., Wilson, J. J., McKay, D., Bump, J. K., Cooper, L. W. & Grebmeier, J. M. (2010). Walruses attack spectacled eiders wintering in pack ice of the Bering Sea. Arctic 63, 53–56. Lowry, D., Wintzer, A. P., Matott, M. P., Whitenack, L. B., Huber, D. R., Dean, M. & Motta, P. J. (2005). Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum. Environmental Biology of Fishes 73, 453–462. Marshall, B. (2011). The Fishes of Zimbabwe and their Biology. Grahamstown: South African Institute for Aquatic Biodiversity. Mehner, T., Ihlau, J., D¨orner, H. & H¨olker, F. (2005). Can feeding of fish on terrestrial insects subsidize the nutrient pool of lakes? Limnology and Oceanography 50, 2022–2031. Oatley, T. B. (1960). Miscellaneous notes of natural history interest. 5. Swallows taken by tigerfish. Lammergeyer 1, 37–38. O’Brien, G. C., Bulfin, J. B., Husted, A. & Smit, N. J. (2012). A comparative behavioural assessment of an established and new tigerfish (Hydrocynus vittatus) population in two artificial impoundments in the Limpopo catchment, Southern Africa. African Journal of Aquatic Sciences 37, 253–263. Pyper, C. (2007). Stillwater trout, tigerfish, Clanwilliam yellows, Garrick, queenfish. In Favoured Flies & Select Techniques of the Experts, Vol. 3 (Meintjes, M. & Pedder, M., eds), pp. 79–86. Johannesburg: Federation of Southern African Flyfishers. Schuster, S., W¨ohl, S., Griebsch, M. & Klostermeier, I. (2006). Animal cognition: how archer fish learn to down rapidly moving targets. Current Biology 16, 378–383. Timmermans, P. J. A. (2001). Prey catching in the archer fish: angles and probability of hitting an aerial target. Behavioural Processes 55, 93–105.
© 2013 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 263–266
