Summary
To protect itself from the extreme heat and dryness of its habitat in summer, Hemilepistus reaumuri must spend most of the time in its burrow. However, to forage it has often to make large excursions. As a rule it is able to return from any point to the entrance of the burrow by the shortest way.
If a returning isopod misses the entrance by a few millimeters, it must search for it. Not until the second antennae have nearly touched the edge of the burrow entrance does an isopod detect it, by means of chemoreceptors in the terminal antennal segment. Even when the entrance is within reach of the antennae occasionally the animal will not detect it.
H. reaumuri searches for the entrance of its burrow in a systematic and successful manner. If the excursion has covered only a short distance, it searches initially in a spiral pattern. If the burrow is not found during this phase the animal extends its range, moving in broad loops and meanders, but returns repeatedly to the starting point of the search.
The problem H. reaumuri must solve in finding its burrow is described in quantitative terms. It is assumed that before the search begins the animal does not know the exact position of the entrance but possesses information about the probability density for this position. The difficulties encountered in detecting the burrow entrance are also taken into account. There is a very small probability that an isopod will detect the entrance if it searches only superficially in the region where the entrance actually is, but this probability increases rapidly with the intensity of search. For this reason it is advantageous for H. reaumuri to return after a while to a region it has already searched without success. The theoretical systematic form of search with the highest probability of success is derived under these conditions.
The search behavior of H. reaumuri is as effective as this systematic form of search. The isopods also follow the most important rules governing the spatiotemporal properties of this pattern. They concentrate their search within a narrowly circumscribed region around the starting point. In all regions further away search would be unprofitable, for the increase in probability of success achieved by searching in these regions as well is too small in comparison with the additional search time required. Because this region continually expands as long as the search is unsuccessful, the isopods search over progressively larger areas until they have reached their goal.
Similar content being viewed by others
References
Claparède E (1903) La faculté d'orientation lointaine. Arch Psychol (Geneva) 2:133–180
Griffin DR (1944) The sensory basis of bird navigation. Q Rev Biol 19:15–31
Heinroth O, Heinroth K (1941) Das Heimfindevermögen der Brieftauben. J Ornithol 89:213–256
Hodge CF (1894) The method of homing pigeons. Pop Sci Monthly 44:758–775
Hoffmann G (1978) Experimentelle und theoretische Analyse eines adaptiven Orientierungsverhaltens: Die ‘optimale’ Suche der Wüstenassel Hemilepistus reaumuri, Audouin und Savigny (Crustacea, Isopoda, Oniscoidea) nach ihrer Höhle. Ph D thesis, Regensburg
Hoffmann G (1983) The random elements in the systematic search behavior of the desert isopod Hemilepistus reaumuri. Behav Ecol Sociobiol 13:81–92
Hoffmann G (1983a) Homing by a systematic search. Proc 8. Cybern Congr (in press)
Koopman BO (1946) Search and screening. Operations Evaluation Group Rep 56, Washington, DC
Linsenmair KE (1972) Die Bedeutung familienspezifischer ‘Abzeichen’ für den Familienzusammenhalt bei der sozialen Wüstenassel Hemilepistus reaumuri Audouin u. Savigny (Crustacea, Isopoda, Oniscoidea). Z Tierpsychol 31:131–162
Linsenmair KE (1979) Untersuchungen zur Soziobiologie der Wüstenassel Hemilepistus reaumuri und verwandter Isopodenarten (Isopoda, Oniscoidea): Paarbindung und Evolution der Monogamie. Verh Dtsch Zool Ges 1979:60–72
Matthews GVT (1971) Vogelflug. Goldmann, München
Rennie J (1835) The faculties of birds. London
Seelinger G (1977) Der Antennenendzapfen der tunesischen Wüstenassel Hemilepistus reaumuri, ein komplexes Sinnesorgan (Crustacea, Isopoda). J Comp Physiol 113:95–103
Stone LD (1975) Theory of optimal search. Academic Press, New York San Francisco London
Wehner R, Srinivasan MV (1981) Searching behaviour of desert ants, Genus Cataglyphis (Formicidae, Hymenoptera). J Comp Physiol 142:315–338
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hoffmann, G. The search behavior of the desert isopod Hemilepistus reaumuri as compared with a systematic search. Behav Ecol Sociobiol 13, 93–106 (1983). https://doi.org/10.1007/BF00293799
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00293799