Available online at www.sciencedirect.com Absence of the tail in female rats disrupts the copulatory pattern of experienced male partners ESTELA CUEVAS * , MAYVI ALVARADO† & PABLO PACHECO†‡ *Centro Tlaxcala de Biologı ´a de la Conducta, Universidad Auto ´ noma de Tlaxcala, Me ´xico yInstituto de Neuroetologı ´a, Universidad Veracruzana, Me ´xico zInstituto de Investigaciones Biome ´dicas, Universidad Nacional Auto ´noma de Me ´xico (Received 26 October 2006; initial acceptance 31 January 2007; final acceptance 8 August 2007; published online 20 February 2008; MS. number: A10603R) Diverse factors such as sex hormones and sensory stimulation, mainly of the perigenital region, influence sexual behaviour of both Wistar male and female rats, Rattus norvegicus. The tail in rats provides important sensory and propioceptive information, which suggests that this part of the body could be relevant during sexual performance. We analysed the repercussion of the absence of the tail on male and female sexual behaviour. In experiment 1, the lack of the tail in males (caudotomized group) did not affect their copu- latory parameters. In comparison with sham and intact groups, they correctly executed the copulatory pattern and deposited the seminal plug into the vagina. Thus, the sensory information given by the tail in males was not relevant for their sexual performance. In experiment 2, the lack of the tail in females did not affect the lordosis quotient in comparison with control females, but it did alter copulatory para- meters of male partners with tails. Although caudotomized females were as attractive as control females, males that mated with caudotomized females performed more mounts, and fewer intromissions, and they had lower intromission rates, longer latencies to ejaculation, longer interintromission intervals and longer postejaculatory intervals than males that mated with control females. These results suggest that the female tail stimulates the perineal area of males, facilitating male copulatory performance, because males that mated with caudotomized females had reduced sexual performance. Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Keywords: copulatory behaviour; ejaculation; intromission; lordosis; mating; mount; Rattus norvegicus; sexual motiva- tion; tail; Wistar rat Sexual behaviour in both male and female rodents involves execution of stereotyped behavioural responses using diverse muscles (Hart & Melese-D’Hospital 1983) and specific brain regions (van Furth et al. 1995; Kondo et al. 1997; Agmo 1999; Liu & Sachs 1999). The sexual display behaviour of male rats is characterized by an arousal phase and a performance phase, although sexual arousal occurs during the performance phase. The first, or ‘precopulatory’, phase includes male recognition of females by olfaction, production of ultrasonic vocaliza- tions and urine marking. The second phase involves rhythmic pelvic movements that may result in insertion of the penis into the vagina. Temporal and spatial pat- terns of both phases can be modulated by sex hormones (Clancy et al. 2000; Huddleston et al. 2003; Bakker et al. 2004) and sensory stimuli (e.g. presence of a receptive female: Hetta & Meyerson 1978; Lo ´ pez et al. 1999; Agmo 2003; female odour: Carr et al. 1965). The mating pattern of the female rat includes attractive, proceptive and receptive (lordosis) behaviours (Komisaruk 1974; Beach 1976; Erskine 1989). Similar to males, female mat- ing behaviour can be regulated by gonadal hormones Correspondence: P. Pacheco, Instituto de Neuroetologı ´a, Universidad Veracruzana, Xalapa, Ver., Me ´xico (email: ppacheco@uv.mx). E. Cue- vas is at the Centro Tlaxcala de Biologı ´a de la Conducta, Universidad Auto ´noma de Tlaxcala, Tlaxcala, Me ´xico, Carretara Tlaxcala/Puebla Km 1.5, C.P. 90110. M. Alvardo is at the Instituto de Neuroetologı ´a, Universidad Veracruzana, Xalapa, Ver., Me ´xico, Carretera Xalapa- Veracruz Km 3.5. 1243 0003e 3472/08/$34.00/0 Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2008, 75, 1243e1251 doi:10.1016/j.anbehav.2007.08.031