Anim. Behav ., 1977, 25,1063-1066

Substrate Feeders sad Facultative Cleaves :Cleaning Behaviour in Some Gulf of California Marine

AnimalsCleaning symbiosis (allogrooming) is an importantinterspecific interaction in the marine environment .Substrate-feeding organisms are particularly well adaptedfor facultative cleaning, the integument of the hostserving as the feeding substratum . Such facultative (part-time) cleaners are non-host specific, to the extent thatthey will attempt to clean the skin of human divers .Juvenile angelfishes (Pomacanthus arcuatus and P. paru) inFlorida waters are reported to clean human divers as wellas other fishes (Brockmann & Hailman 1976). I observedsimilar behaviour in a juvenile P. zonipectus in the Gulfof Cali fornia, which nipped at damaged tissue around awound on my ankle. The encounter was brief, but thefeeding movements and postures were similar to thoseexhibited by this species when feeding on sponges,algae, and other benthic organisms in nature and inaquaria (Reynolds & Reynolds 1977), and is similar tothat of other Pomacanthus species (Brockmann & Hailman1976). I have not seen these clean other fish in the field,but did find a ctenoid scale in the stomach of an adult inan earlier feeding study (Reynolds & Reynolds 1977) .Randall & Hartman (1968) report the presence ofcrustacean ectoparasites of reef fishes in stomachs ofjuvenile Pomacanthus and Holacanthus angelfishes fromthe West Indies.

Other Gulf of California fishes which I have observedto clean humans by gently nibbling at the skin or tuggingat body hairs are the wrasse 7halassoma lucasanum(Labridae), the goby Elacatinus digueti (Gobiidae),juvenile sergeant majors (Abudefduf trosche, Pomacen-tridae), and juvenile mojarras (Eucinostomus sp.,Gerreidae): see Thomson & McKibbin (1976) foridentification and descriptions. I have also observedcleaning behaviour in two species of prawns (Palaemon-idae), which I believe to be the first such behaviourreported for this euryhaline (Reynolds 1975) family .In a freshwater spring entering an intertidal pool at thesmall embayment of El Coyote off the larger BahiaConcepcion, Baja California Sur, I was cleaned byfreshwater prawns of the genus Macrobrachium, identi-fiable by the characteristic very long chelipeds . Approach-ing me cautiously as I sat in the shallow pool, these firsttested my skin with the extended chelae, and then havingdiscovered the area of keratinized cuticle around myfingernails, applied the mouthparts directly to the cuticleand gave me a thorough manicure, the larger ones fendingoff smaller individuals with the extended long chelipeds .They persisted in this until I moved .

At another site further south in Baja California (PlayaEscondida Blanca, near Ligui south of Puerto Escondido),I was similarly cleaned by groups of smaller Palaemonritteri tidepool prawns. The behaviour was similar,allowing for the much smaller chelipeds . To get leverage,these small prawns would frequently seize a hair on theback of the hand and then jump backwards (as in theircharacteristic escape response) holding onto it in anunsuccessful attempt to pull it out (Elacatlnus diguetigobies also try to pull out hairs, which must resembleectoparasites) . The P. ritteri prawns eventually resortedto manicuring the cuticle around my nails as did Macro-brachium. The chewing action of the mouthparts couldbe felt but was quite gentle and painless . The gentle

SHORT COMMUNICATIONS

1063

tactile stimulation was in fact quite pleasant, and appar-ently serves as a positive reinforcer for non-humanspecies as well (Losey & Margules 1974) . Considerabledead skin (which had been softened by immersion in saltwater) was removed. During this time, small sergeant

nibbled in wfeltpool abump)ilat mr s

temporarilyfrightening away the P. ritteri.

My observations suggest that these facultative cleanersregard as a suitable feeding substratum any non-movingsurface, animate or inanimate, offering edible material.That non-marine species such as humans are cleaned isindicative of the facultative and non-specific nature ofcleaning behaviour in these species. Substrate-feedinghabits may constitute pre-adaptive traits from whichmore specialized cleaning behaviour might evolve .

WILLIAM W. REYNOLDSBiology Department,Pennsylvania State University,Wilkes-Barre,Pennsylvania 18708 .ReferencesBrockmann, H. J. & Hailman, J . P . 1976. Fish cleaning

symbiosis : notes on juvenile angelfishes (Poma-canthus, Chaetodontidae) and comparisons withother species . Z. Tlerpsychol., 42,129-138 .

Losey, G. S . Jr & Margules, L . 1974. Cleaning symbiosisprovides a positive reinforcer for fish . Science,N. Y., 184, 179-180.

Randall, J. E. & Hartman, W. D. 1968 . Sponge-feedingfishes of the West Indies . Marine Blol., 1, 216-225 .

Reynolds, W. W. 1975 . Salinity tolerance of the tidepoolshrimp Palaemon ritteri Holmes . Comp. Biochem.Physiol., 52A, 665-667 .

Reynolds, W. W. & Reynolds, L. J. 1977. Observationson food habits of the angelfishes Pomacanthuszonipectus and Holacanthus Passer in the Gulf ofCalifornia. Calif. Fish Game, 63, 124-125.

Thomson, D. A. & McKibbin, N . 1976. Gulf of CaliforniaFishwatcher's Guide. Tucson: Golden Puffer Press.

(Received 11 March 1977 ; revised 18 April 1977 ;MS. number : As-12)

Flocking Behaviour and Territorial CompetitorsThe adaptive value of flocking behaviour has receivedmuch attention with the purported advantages tendingto fall into two broad categories : (1) protection frompredators (e .g. Goss-Custard 1970 ; Pulliam 1973 ;Treisman 1975a, b) and (2) enhanced feeding efficiency(e.g. Murton 1971 ; Cody 1971 ; Ward & Zahavi 1973 ;Thompson et al. 1974). Members of a flock do not foragein a competitive vacuum but must often cope directlywith interspecific competitors (contest or interferencetype competition) . For example, large flocks of cedarwaxwings (Bombycilla cedrorum) are common in thepiedmont region of South Carolina during the winter .Patches of berry-laden trees such as holly (Ilex) andflowering dogwood (Cornus forida) as well as Pyracanthashrubs are popular food sources to these birds. At thesame time and over the same area mockingbirds (Mimuspolyglottos) maintain territories within which is locatedthe fruit so attractive to the waxwings ; a resource vigor-ously defended both intra- and interspecifically by the