It is an NP-complete problem to decide whether a graph contains a spanning tree with no vertex of degree 2. We show that these homeomorphically irreducible spanning trees are contained in all graphs with minimum degree at least c f i and in triangulations of the plane. They are nearly present in all graphs of diameter 2. They do not necessarily occur in r-regular or r-connected graphs.

No abstract

Methods. Nine feral horses were darted from the ground with 60 mg of medetomidine and 1500 mg of tiletamine-zolazepam. The effects of medetomidine were reversed with 50-100 mg of atipamezole 30-40 minutes post induction (IV/IM). Physiological variables monitored during anaesthesia were heart rate, respiratory rate, temperature and oxygen haemoglobin saturation (S p O 2 ). 2Key results. All horses were successfully immobilised with between one and three darts (n = 9). The mean dose of medetomidine was 0.15 ± 0.01 mg kg -1 (SEM) and tiletaminezolazepam was 3.61 ± 0.16 mg kg -1 . Mean time from darting to lateral recumbency was 13 ± 2.7 min, and mean recumbency time was 54 ± 13 min. Vital signs for all anaesthetised animals remained within normal range during anaesthesia, with the exception of one animal displaying a transient drop in S p O 2 . No mortalities were encountered.Key conclusions. The combination of medetomidine and tiletamine-zolazepam provided adequate anaesthesia in feral horses in the field for application of GPS collars.Implications. Although a limited number of horses were immobilised, this study shows that medetomidine and tiletamine-zolazepam provides effective short-term anaesthesia for feral horses, providing a practical and field-accessible capture technique. This method could also be applied to other management actions requiring safe and humane capture of feral horses.