Vibrating aggression: Spider males perform an unusual assessment strategy during contest displays

A recurrent question in animal contests is whether individuals adopt a self or mutual assessment rule to decide to withdraw from a contest. However, many empirical studies fail to find conclusive support for one of these two possibilities. A possible explanation is that assessment strategies vary between individuals. In the contests of the orb-web spider Trichonephila clavipes, males perform a vibrational display on webs that may escalate to physical contact. Since all individuals perform the vibrational phase and only some of them escalate, we proposed two hypotheses: 1) all individuals perform mutual assessment during the vibrational phase, or 2) some individuals that do not escalate adopt self-assessment, while individuals that escalated adopt mutual assessment. To evaluate these hypotheses, we investigated the relationship between the duration of the vibrational phase and frontal leg length (a proxy of male fight capacity) of loser and winner males in contests that escalated and did..., Study area
We conducted this study between December 2018 to March 2019 and between February 2021 and March 2021 in the Ecological Station of the Federal University of Minas Gerais (19° 52’ 25’’ S, 43° 58’ 21’’ W), Minas Gerais State, Brazil. The Ecological Station is a 114 ha area composed of a mixture of semi-deciduous Atlantic forest, Brazilian savanna (i.e., Cerrado), and invasive plant species (Antonini and Martins 2003). Individuals of T. clavipes are abundant in this area between December and June (Almeida and Peixoto 2021; Silva et al. 2021).
Field sampling
We searched for female webs along three trails of approximately 20 m, 300 m, and 400 m in length. We selected female webs with mature females or females in their last instar because males of T. clavipes defend females in both ontogenetic stages (Almeida and Peixoto 2021). We considered females that had a swollen and sclerotized epigynum with two distinct copulatory openings to be mature (Higgins 2000; Rittschof 2011), and fema..., , # Vibrating aggression: spider males perform an unusual assessment strategy during contest displays

[https://doi.org/10.5061/dryad.bg79cnpjg](https://doi.org/10.5061/dryad.bg79cnpjg)

In this study we evaluated whether an initial non-contact vibrational interaction performed by males of the spider *T. clavipes* represents a contest phase in which all rivals perform mutual assessment or a mixture of self- and mutual assessors. If our hypothesis that all rivals perform mutual assessment was correct, we expected to find a positive relationship between the duration of the vibration interaction and losers frontal leg length and a negative relationship between the duration of the vibrational interaction and frontal winners leg length. We would also expect a similar R2resid for the model testing the relationship between duration and winners front leg length for non-escalated fights when compared to the same model considering only fights that escalated. On the other hand, if our hypothesis abo...