Be meek or be bold? A colony-level behavioural syndrome in ants.

Consistent individual variation in animal behaviour is nearly ubiquitous and has important ecological and evolutionary implications. Additionally, suites of behavioural traits are often correlated, forming behavioural syndromes in both humans and other species. Such syndromes are often described by testing for variation in traits across commonly described dimensions (e.g. aggression and neophobia), independent of whether this variation is ecologically relevant to the focal species. Here, we use a variety of ecologically relevant behavioural traits to test for a colony-level behavioural syndrome in rock ants (Temnothorax rugatulus). Specifically, we combine field and laboratory assays to measure foraging effort, how colonies respond to different types of resources, activity level, response to threat and aggression level. We find evidence for a colony level syndrome that suggests colonies consistently differ in coping style--some are more risk-prone, whereas others are more risk-averse. Additionally, by collecting data across the North American range of this species, we show that environmental variation may affect how different populations maintain consistent variation in colony behaviour.

Treatment of infected knee arthroplasty.

Forty-eight patients with 51 infected knee arthroplasties were treated at the authors' institution between 1973 and 1986 and followed for 5.5 (range, 0-14) years. Six methods to treat the infections were employed: antibiotics only, soft-tissue surgery, removal of the prosthesis, revision arthroplasty, arthrodesis, and amputation. Failure of the initial surgical treatment led to second revision surgery in 20 patients. At the follow-up examination, three patients (five knees) had died from septic complications and two patients had had above-knee amputation. Two of 32 patients had been successfully treated with antibiotics with no additional surgery. Four patients had successful soft-tissue surgery. Following removal of the prosthesis, the infection healed in four patients. In 12 of 19 patients (13 knees) with revision arthroplasty the infection healed, but only seven of these had functioning prostheses. The infection healed in all but one of the 21 patients with arthrodeses, and all but two were fused. Infected compartmental prostheses with good bone stock can be treated with an exchange arthroplasty using a two-stage procedure with tricompartmental revision prostheses. Otherwise, an arthrodesis using a two-stage procedure is recommended for the treatment of infected knee arthroplasty.