Wolfgang Wickler

The erect 'penis' is a flag of submission in a female-dominated society: greetings in the Serengeti spotted hyaenas

In East Africa, spotted hyenas live in large clans in a highly structured society dominated by females. A clan is a fission-fusion society where members are often solitary or in small groups. Spotted hyenas have a ritualized greeting during which two individuals stand parallel and face in opposite directions. Both individuals usually lift their hind leg and sniff or lick the anogenital region of the other. The unique aspect of greetings between individuals is the prominent role of the erect ‘penis’ in animals of both sex. Female spotted hyenas have fused outer labiae and a ‘pseudo-penis’ formed by the clitoris which closely resembles the male penis and can be erected. During greetings subordinates signalled submission with gestures which were not necessarily reciprocated by the dominant participant. Asymmetries were most pronounced in greetings between adult females where the probability of asymmetries increased with the divergence in rank between partners. Greetings between adult females and males were uncommon and restricted to males above median rank, principally the alpha male. Models of primate affiliative behavior assume that benefits derived from social relationships with different individuals are not equal and that individuals are selected to maximize the benefits they receive from social relationships with others. The observed distribution of greetings between partners of different rank matched the predictions of these models. An examination of non-adaptive hypotheses on the evolution of the ‘pseudo-penis’ demonstrated that the conventional scenario linking (initial) virilization of female genitalia with selection for female dominance does not explain either the initial virilization, nor the evolution of the ‘pseudo-penis’ to its current form and use. We sketch a new scenario that links (1) initial virilization to the occurrence of neonatal siblicide amongst members of a twin litter, and (2) costs of maintenance, ‘pseudo-penile’ control over copulation and male submission. Our analysis confirms previous adaptive hypotheses on the function of the ‘pseudo-penis’ in greetings and suggests new hypotheses to account for hitherto unexplained features.

Über den taxonomischen Wert homologer Verhaltensmerkmale

ZusammenfassungDas Homologisieren ist eine Methode, die mit empirisch erarbeiteten Kriterien den Nachweis führt, daß die Ähnlichkeit zweier Merkmale auf weitergegebener Information beruht, also weder zufällig noch unabhängig zustande kam. Information kann von lebenden Systemen auf zwei Wegen weitergereicht werden, nämlich durch das Genom und durch Tradition. Das Homologisieren einzelner Merkmale ist das wichtigste Verfahren zur Bestimmung des Verwandtschaftsgrades der Merkmalsträger. Der Schluß auf ihre Verwandtschaft ist jedoch nur dann berechtigt, wenn es sich um Merkmale handelt, die im Genom und damit untereinander verankert, also im Sinne der Ethologie „angeboren” sind. Mit Hilfe der Homologiekriterien ist die strenge Unterscheidung angeboren-erworben nicht möglich, sie muß gesondert getroffen werden. In der Merkmalsphylogenie tritt diese Schwierigkeit nicht auf. — Einige methodische Schwierigkeiten, die sich nun ergeben, werden kurz besprochen.

Pharmacophagy in grasshoppers?. Zonocerus attracted to and ingesting pure pyrrolizidine alkaloids

Zonocerus elegans has been found to be attracted to pure pyrrolizidine alkaloids and to ingest them. This finding makes the species likely to be pharmacophagous; also, it might provide means of controlling Zonocerus, and it indicates the importance of olfaction for localizing and recognizing host‐plants in grasshoppers.

The protective function of the compact silk nest of social Stegodyphus spiders (Araneae, Eresidae)

SummaryThis study investigates the suggested protective function of the compact silken nest of two species of social Stegodyphus spiders (S. dumicola and S. mimosarum), as a possible ultimate factor for their sociogenesis. Being inhabitants of African dry thornbush country, these spiders are endangered by overheating and desiccation. In the laboratory, both species were found to avoid temperatures >40° C. In the field, temperature in the nest between 7:00 and 21:00 h tends to be higher than air-temperature outside, and between 13:00 and 15:00 h even tends to exceed 40° C. The nest thus is of no value in temperature regulation. Nor is it effective in protecting the spiders from desiccation: Both species have a body water content of 65.2±3.8% and are extremely desiccation resistant; they survived 9 days at 37°C in an exciccator with P2O5, with a daily average % liveweight reduction of 4.94(±1.1). In the field, relative humidity inside the nest between 11:00 and 19:00 h tends to be lower than that of the air outside. Inspection of burnt areas showed that the nest does not protect the spiders from bushfire. The nest does protect from wind, hail, and direct sun-radiation; but available natural retreats, or a simple silken shield, or the funnel-shaped silk tube inhabited by solitary Stegodyphus, have the same effect.

Population history in social spiders repeated: colony structure and lineage evolution in Stegodyphus mimosarum (Eresidae).

Social cooperative spiders from diverse taxonomic families share life‐history and demographic traits, including highly inbred colony structure. The combination of traits suggests constrained pathways for social evolution in spiders. The genus Stegodyphus has three independently evolved social species, which can be used as replicate samples to analyse population constraints in evolutionary time. We tested colony structure and population history of the social S. mimosarum from South and East Africa using mitochondrial DNA variation, and we compared the results to published data for the independently evolved social congener S. dumicola. S. mimosarum had many and diverse haplotypes (5–7% sequence divergence for ND1) but colonies were monomorphic and genealogically similar haplotypes occurred in abutting regions. These findings are nearly identical to results for S. dumicola and imply similar colony‐level processes over evolutionary time in independently evolved social species. These population dynamics are discussed with respect to the apparent lack of cladogenesis in social spiders.

Ontogeny of song in captive duet-singing slate-coloured boubous (Laniarius funebris). A study in birdsong epigenesis

Ontogeny of song was studied in 11 L. funebris reared in captivity under different learning regimes. Song types usually were learned from conspecific tutors: Males learned from male, females from female tutors. In exceptional situations song types may be learnt from the other sex, proving an ability to produce song of both sexes. Birds reared without tutors nevertheless produced some species-typical song in generalized form, suggesting an innate predisposition for these vocalizations. Once established during the first 6-8 months of life, individual repertoires remained unchanged for years. Pair mates regularly dueted. Neither random pairings nor mate exchanges revealed repertoire alteration in mates. Neither misdeveloped nor reduced song repertoires hampered successful breeding in captivity.

Bi-Directional Sexual Dimorphisms of the Song Control Nucleus HVC in a Songbird with Unison Song

Sexually dimorphic anatomy of brain areas is thought to be causally linked to sex differences in behaviour and cognitive functions. The sex with the regional size advantage (male or female) differs between brain areas and species. Among adult songbirds, males have larger brain areas such as the HVC (proper name) and RA (robust nucleus of the arcopallium) that control the production of learned songs. Forest weavers (Ploceus bicolor) mated pairs sing a unison duet in which male and female mates learn to produce identical songs. We show with histological techniques that the volume and neuron numbers of HVC and RA were ≥1.5 times larger in males than in females despite their identical songs. In contrast, using in-situ hybridizations, females have much higher (30–70%) expression levels of mRNA of a number of synapse-related proteins in HVC and/or RA than their male counterparts. Male-typical and female-typical sexual differentiation appears to act on different aspects of the phenotypes within the same brain areas, leading females and males to produce the same behaviour using different cellular mechanisms.

Structure, geography and origin of dialects in the traditive song of the Forest weaver Ploceus bicolor sclateri in Natal, S. Africa

From a 21-year-long combined field and laboratory study we describe the general song structure and local song dialects of this species. These dialects differ in syntactic and phonological charateristics. Within its first 24 months the individual learns a song from its parents and keeps that song constant throughout life. In free-living populations dialects remained constant over the total study period. We could exclude that the dialects are an acoustic window phenomenon. We found individual song variations within dialects which suggest a derivation of local dialects from family-specific songs, enhanced by man-induced habitat fragmentation.

Species cohesion despite extreme inbreeding in a social spider

Colonial social spiders experience extreme inbreeding and highly restricted gene flow between colonies; processes that question the genetic cohesion of geographically separated populations and which could imply multiple origins from predecessors with limited gene flow. We analysed species cohesion and the potential for long‐distance dispersal in the social spider Stegodyphus dumicola by studying colony structure in eastern South Africa and the cohesion between this population and Namibian populations previously published. Data from both areas were (re)analysed for historic demographic parameters. Eastern South African S. dumicola were closely related to an east Namibian lineage, showing cohesion of S. dumicola relative to its sister species. Colony structure was similar in both areas with mostly monomorphic colonies, but haplotype diversity was much reduced in eastern South Africa. Here, the population structure indicated recent population expansion. By contrast, Namibia constitutes an old population, possibly the geographic origin of the species. Both the comparison of the eastern South African and Namibian lineages and the distribution within eastern South Africa show the potential for long‐distance dispersal in few generations via colony propagation.

Die Evolution von Mustern der Zeichnung und des Verhaltens

Das Wort „Muster“ bezeichnet ein in geordneter Weise aus Teilen zusammengesetztes System. Aus dem Angelsachsischen ist z. B. durch das Wort „behaviour pattern“ der Oberbegriff „Muster“ auch bei uns fur Ablaufsformen (Gesange, Bewegungsweisen) zustandig geworden, deren Teile nicht nur raumlich, sondern zeitlich gegeneinander abgegrenzt sind, also nicht zugleich, sondern nacheinander wahrnehmbar werden. Die Alltagssprache kennt vorwiegend optische Muster, wie sie uns am auffalligsten an Bluten, Schmetterlingen, Zierfischen usw. entgegentreten. Gerade bei Zierfischen mit ihrem Farbwechsel haben wir es dann aber mit mehrererlei Musterbegriffen zu tun, je nachdem ob wir nur das jeweils sichtbare Farbkleid oder die Gesamtheit aller Farbkleider oder den Farbwechsel meinen. Bislang wird hier jedoch kein Unterschied gemacht; „Muster“ ist vorerst nur eine Bezeichnung, mit der wir ausdrucken, das die willkurlich gewahlte Gesamterscheinung aus Teilen zusammengesetzt ist. Oft genug werden nicht einmal diese Bauteile eigens bezeichnet; wichtig ist zunachst nur, das wir glauben, sie gehorten zusammen.