Hunting Strategies of a Lake Malawi Cichlid with Reverse Countershading Author(s): Jay R. Stauffer, Jr., Elisabeth A. Half and Ryan Seltzer Source: Copeia, Vol. 1999, No. 4 (Dec. 17, 1999), pp. 1108-1111 Published by: American Society of Ichthyologists and Herpetologists (ASIH) Stable URL: http://www.jstor.org/stable/1447987 Accessed: 02-07-2015 19:42 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Society of Ichthyologists and Herpetologists (ASIH) is collaborating with JSTOR to digitize, preserve and extend access to Copeia. http://www.jstor.org This content downloaded from 131.128.109.174 on Thu, 02 Jul 2015 19:42:41 UTC All use subject to JSTOR Terms and Conditions Copeia, 1999(4), pp. 1108-1111 Hunting Strategies of a Lake Malawi Cichlid with Reverse Countershading J ay R. S t a u f f e r J r ., E l is a b e t h A . H a l e , a n d R yan S e l t z e r Tyrannochromis macrostoma (Regan), a haplochromine cichlid fish endemic to Lake Malawi, Africa, exhibits reverse countershading. It attacks potential prey fishes from an upright, sideways (90° rotation from an upright position), or upside-down (180° rotation from an upright position) positions. Seventy percent of its attacks are from a sideways position. Whenever it was observed attacking from an upside-down po­ sition, its prey was stationed below the attacker. When attacking from a sideways position, its prey was below the attacker 25% of the time and on the same plane 75% of the time. When attacking from a normal position, its prey was below the T. macrostoma 82% of the time and on the same plane 18% of the time. Data presented herein lend credence to the self-shadow concealment explanation for the selection of countershading. Tyrannochromis nigriventer Eccles, a closely related species, does not display reverse countershading but occasionally attacks from an upside-down position. OUNTERSHADING denotes that one side pothesis that DPD serves to increase foraging C of an animals’ body is darker than the oth­ efficiency in predatory cichlids that hunt active er (Thayer, 1896). Countershading occurs in mobile prey. various vertebrate groups including fishes (Bri- Alternative explanations to the self-shadow chard, 1978; Konings, 1987), birds (Butcher concealment (SSC) hypothesis for DPD exist. and Rohwer, 1989), and mammals (Strahan, Dorsal pigmentary darkening may increase 1983). In many of these dichromatic organisms, abrasion resistance in nonaquatic species, shield the dorsum is the more darkly pigmented side, against ultraviolet light, or be important in ther­ which is termed dorsal pigmentary darkening moregulation (Kiltie, 1988). Furthermore, the (DPD). Such a pigment pattern may be impor­ dorsal surface may be the primary side exposed tant in shape concealment via self-shadow con­ by prey to predators or by predators to prey; cealment (SSC) because, if the dark side of the thus the only side for which camouflaging col­ body is oriented to the light source, shadows on oration is important (Kiltie, 1988). the body are concealed (Kiltie, 1988). Evidence Hypotheses that countershading is important of the benefits of DPD is circumstantial and in­ in shape concealment and camouflage can be cludes the following: (1) DPD is present in evaluated by examining the behavior and life many taxa; (2) the more darkly pigmented sides history of those fishes that exhibit reverse coun­ are usually on the side facing the light source; tershading or ventral pigmentary darkening and (3) DPD camouflages organisms to the hu­ (VPD) to see whether their behaviors are dif­ man eye (Kiltie, 1988). Ruiter (1956) provided ferent from those fishes that show DPD. Certain some experimental evidence in support of SSC catfishes in the family Mochokidae swim upside- when he showed that inverted caterpillars were down at night and are characterized by VPD, more susceptible to predation by birds than up­ including Synodontis nigriventris David and Hem- right caterpillars. isynodontis membranaceus Geoffroy Saint-Hilaire In fishes, pigmentation may be related to cer­ (Daget, 1948; Poll, 1971; Nagaishi et al., 1989). tain hunting strategies. For example, in the While swimming upside-down, these species Lake Tanganyika cichlid, Lepidiolamprologus pro- feed on plankton and fine detritus from the wa­ fundicola (Poll), there are two distinct color ter’s surface (Bishai and Abu Gideiri, 1963; morphs, pale and dark. The dark color form Holden and Reed, 1972; Lowe-McConnell, frequently attacks prey from shaded areas, 1975). VPD may minimize predation of these whereas the pale form initiates attacks from fishes, when they are in the upside-down pos­ open water (Kohda and Hori, 1993). Compari­ ture (Chapman et al., (1994). sons of 19 taxa of carnivorous Lake Tanganyika Increased respiratory efficiency also has been cichlids showed that dichromatic taxa generally linked with swimming upside-down (Holden chase active prey, whereas monochromatic and Reed, 1972; Roberts, 1975). Chapman etal. forms feed on sessile or sluggish prey (Kohda (1994) provided evidence that suggested that 5. and Hori, 1993). Such evidence supports the hy­ nigriventris, which exhibits VPD, expended less © 1999 by the American Society of Ichthyologists and Herpetologists This content downloaded from 131.128.109.174 on Thu, 02 Jul 2015 19:42:41 UTC All use subject to JSTOR Terms and Conditions STAUFFER ET AL.—HUNTING STRATEGIES OF T. MACROSTOMA 1109 paper is to describe the hunting behavior of Tyr­ annochromis macrostoma (Regan), a haplochrom- ine cichlid endemic to Lake Malawi that exhib­ its VPD (Fig. 1). M a t e r i a l s a n d M e t h o d s From 11 March to 1 April, 1985, observations on the feeding behavior of 33 T. macrostoma were recorded while SCUBA diving at Mitande Rocks, Cape Maclear, Lake Malawi (14°05'S, 34°54'E). Additionally, we were able to observe the attack sequence of three Tyrannochromis ni- griventer Eccles, a species that does not exhibit VPD. Fifteen-minute focal samples were con­ ducted; however, some observation periods were interrupted because the fish disappeared into a cave or was lost among the rocks (Table 1). To minimize disturbance, the diver (JRS) watched the fish from 5 m behind and 2 m above. While observing the fish, the following events were recorded: the number of times these two species hovered sideways (90° rotation from an upright position not followed by an at­ tack) , the number of times they hovered upside- down (180° rotation from an upright position not followed by an attack), the number of times they attacked from an upright position, the num ber of times they attacked from a sideways position, the number of times they attacked from an upside-down position, and the total time that each fish was observed. As the fish swam through the water column, it would some­ times pause in an upright position. Because it was not possible to determine whether the fish was observing a potential prey item or just rest­ ing, hovers in an upright position were not re­ corded. Fig. 1. Tyrannochromis macrostoma swimming in a normal position (A), turning 180° (B), and swimming Attacks were defined as a sudden fast move­ away with a fish in its mouth (C). ment toward a potential prey. An attack was sometimes initiated from a hovering position, and sometimes it was an extension of a swim­ energy while swimming upside-down at the wa­ ming/searching pattern. Because it was difficult ter’s surface than did Synodontis afrofischeri Hil- to determine whether the attack was successful, gendorf, which swims in an upright position success was not recorded. and does not display VPD. The purpose of this From January to February 1995, 46 T. macro- Table 1. Summary of the Number of Attacks and Hovers Observed for Tyrannochroms macrostoma a t M i­ tande Rocks, Cape M aclear, Lake Malawi, M alawi, Africa. Number of Tot. min. of obs. Total attacks Total attacks Total attacks Total hovers Total hovers Time of day T. macro. per fish upside-down sideways normal upside-down sideways 0800-1200 14 15 19 44 2 18 110 1200-1630 10 15 4 26 0 5 140 0800-1630 4 10-11 0 10 0 1 22 0800-1600 5 3-6 2 8 1 2 15 Totals 33 25 88 3 26 287 This content downloaded from 131.128.109.174 on Thu, 02 Jul 2015 19:42:41 UTC All use subject to JSTOR Terms and Conditions 1110 COPEIA, 1999, NO. 4 Table 2. Summary of Attacks Recorded from Vid­ while following T. macrostoma with a Nikon 35 eo Tapes of Tyrannochromis macrostoma at Mazinzi mm underwater camera, a successful upside- Reef, Lake Malawi, Malawi, Africa. down attack was observed (Fig. 1). Videos recorded at Mazinzi Reef indicated Attacks No. upside- Attacks Attacks that T. macrostoma would position itself approx­ Time T. macro. Total time aown sideways normal imately 2-10 cm above the rock substratum. 0700-1200 28 5:04:33 4 11 10 Many of the attacks occurred when T. macrosto­ 1201-1600 18 2:19:47 1 5 1 ma swam over a discontinuity with an immediate drop greater than 1 m in the substratum. When Total 46 7:24:20 5 16 11 T.