Searching behaviour of desert ants, genusCataglyphis (Formicidae, Hymenoptera)
- 661 Downloads
If a homing ant (Cataglyphis bicolor,C. albicans) gets lost, it does not perform a random walk but adopts a stereotyped search strategy. During its search the ant performs a number of loops of ever-increasing size, starting and ending at the origin and pointing at different azimuthal directions. This strategy ensures that the centre area where the nest is most likely to be, is investigated most extensively.
After one hour of continuous search the ant's search paths cover an area of about 104 m2. Nevertheless, the system of loops performed during this time is precisely centred around the origin. The ant's searching density does not depend on the azimuthal direction around the origin but only on the distance from the origin. It rapidly decreases with increasing distance.
The ant's searching pattern can be characterized by two functions: thed/t-function correlating distance (d) with time (t), and theα/t-function correlating azimuthal direction (α) with time. If fixes of the ant's position are taken every 10 s, the vectors pointing from the origin to successive fixes change their lengthsd systematically (α/t-function) and their directionsα randomly (α/t-function). What is especially characteristic of the ant's searching pattern is the oscillatingd/t-function which clearly demonstrates that the searching ant repeatedly returns to the origin, even after it has walked, within one hour, along a search trajectory of more than 1 km (the latter number refers toC. albicans-A). The ant's walking speed does not change within a search time of 1 h.
The distribution of changes in direction between successive segments of a search path,β, is usually unimodal with a mean of 0°, if complete search paths are considered. Nevertheless, within smaller periods of time, especially during the initial portions of the search the integrated angleβ may continuously change in the same direction. Such portions of the search crudely resemble a spiral which alternately expands and contracts.
Although all 3 species ofCataglyphis studied in this paper adopt the same general search strategy, there are some differences in the fine structure of the search:C. albicans-A departs further from the origin than any other species, and performs the most rapid turns. The tendency towards spiralling is most pronounced inC. albicans-B.
An efficient searching strategy is formulated, based on purely theoretical grounds. It is assumed that when the search begins the probability density function (PDF) for the location of the nest is Gaussian in two dimensions (a priori PDF). It is further assumed that the ant can never becompletely certain that a given area has been fully explored, so that it is only theprobability of encountering the nest within a certain region that decreases as the time spent in searching this region increases. Thus, the most promising region to search is specified by an a posteriori PDF which takes the ant's past performance into account.
A computer model is presented that searches in optimum fashion, as proposed above. In the model, motion of the ant is characterized in terms of radial and tangential components, with the tangential component varying randomly and the radial component varying according to the a posteriori PDF. The model successfully describes what the ants are actually doing (e.g., compare Figs. 17 and 18 with Fig. 3, Figs. 19 and 20 with Figs. 8–10, and Fig. 21a and b with Figs. 4 and 5), indicating that the searching behaviour ofCataglyphis is geared to find the nest as quickly as possible.
KeywordsProbability Density Function Probability Density Function Tangential Component Searching Behaviour Azimuthal Direction
probability density function
Unable to display preview. Download preview PDF.
- Alcock J (1976) The behaviour of the seed-collecting larvae of a carabid beetle (Coleoptera). J Nat Hist 10:367–375Google Scholar
- Brun R (1914) Die Raumorientierung der Ameisen. Fischer, JenaGoogle Scholar
- Cornetz V (1914) Les explorations et les voyages des fourmis. Flammarion, ParisGoogle Scholar
- Cramer H (1946) Mathematical methods of statistics. Princeton University Press. PrincetonGoogle Scholar
- Duelli P (1975) A fovea for e-vector orientation in the eye ofCataglyphis bicolor (Formicidae, Hymenoptera). J Comp Physiol 102:43–56Google Scholar
- Dueili P, Wehner R (1973) The spectral sensitivity of polarized light orientation inCataglyphis bicolor (Formicidae, Hymenoptera). J Comp Physiol 86:37–53Google Scholar
- Görner P, Zeppenfeld C (1981) The runs ofPardosa amentata (Araneae, Lycosidae) after removing its cocoon. 8. Int. Arachnologentagung, Graz (in press)Google Scholar
- Harkness MLR, Harkness RD (1976) Searching procedure in an ant (Cataglyphis bicolor Fab.). J Physiol 263:268P-269PGoogle Scholar
- Harkness RD, Wehner R (1977)Cataglyphis. Endeavour, N.S. 1:115–121Google Scholar
- Peckham GW, Peckham EG (1898) On the instincts and habits of solitary wasps. Wis Geol Nat Hist Surv Bull 2, Sci Ser 1, 2:1–148Google Scholar
- Peckham GW, Peckham EG (1905) Wasps, social and solitary. Constable, WestminsterGoogle Scholar
- Pyke GH, Pulliam HR, Charnov EL (1977) Optimal foraging: a selective review of theory and tests. Q Rev Biol 52:137–154Google Scholar
- Santschi F (1913) Comment s'orientent les fourmis. Rev Suisse Zool 21:347–426Google Scholar
- Santschi F (1929) Etude sur lesCataglyphis. Rev Suisse Zool 36:25–70Google Scholar
- Stone LD (1975) Theory of optimal search. Academic Press, New YorkGoogle Scholar
- Turner CH (1907) The homing of ants. J Comp Neurol Psychol 17:367–434Google Scholar
- Waddington KD, Holden LR (1979) Optimal foraging: on flower selection by bees. Am Nat 114:179–196Google Scholar
- Wehner R (1972) Visual orientation performances of desert ants,Cataglyphis bicolor, towards astromenotactic directions and horizon landmarks. In: Galler SR et al (eds) Proc AIBS Symp Animal Orientation and Navigation US Gov Print Off, Washington, pp 421–436Google Scholar
- Wehner R (1976) Polarized-light navigation by insects. Sci Am 235/1:106–115Google Scholar
- Wehner R (1981) Spatial vision in arthropods. In: Autrum H (ed) Handbook of sensory physiology, vol VII/6C. Springer, Berlin Heidelberg New York (in press)Google Scholar
- Wehner R, Flatt I (1972) The visual orientation of desert ants,Cataglyphis bicolor, by means of terrestrial cues. In: Wehner R (ed) Information processing in the visual system of arthropods. Springer, Berlin Heidelberg New York, pp 295–302Google Scholar
- Wehner R, Räber F (1979) Visual spatial memory in desert ants,Cataglyphis bicolor (Hymenoptera: Formicidae). Experientia 35:1569–1571Google Scholar
- Wehner R, Brunnert A, Herrling PL, Klein R (1972) Periphere Adaptation und zentralnervöse Umstimmung im optischen System vonCataglyphis bicolor (Formicidae, Hymenoptera). Rev Suisse Zool 79:197–228Google Scholar
- Weyrauch WK (1935) Untersuchungen und Gedanken zur Orientierung der Arthropoden. 8. Teil: Die üblichsten Wege, auf denen die Tiere ihre Umgebung durchsuchen. Zool Jahrb Abt Syst Oekol Geogr Tiere 66:401–424Google Scholar