Never smile at a crocodile: Gaping behaviour in the Nile crocodile at Ndumo Game Reserve, South Africa.

Gaping is a regularly observed behaviour in crocodilians globally but is still poorly understood in relation to external variables which could trigger this behaviour. The occurrence of gaping behaviour was investigated in a large wild population of Nile crocodiles (Crocodylus niloticus) during the dry and wet seasons at Nyamithi Pan, Ndumo Game Reserve, South Africa. This is one of the longest crocodile gaping behaviour studies conducted in the wild, with 300 h of observations conducted over two seasons resulting in 1120 gaping behaviours recorded. The most common size class observed was between 1.5 and 2.5 m (n = 697), which accounted for 62.2% of the gaping observations. A significant decrease in gaping duration was observed as ambient temperatures increased, and the gape duration was longer at a higher degree angle. In addition, an increase in gape duration was observed as the number of neighbouring crocodiles increased. These results suggest gaping behaviour occurs when there are other crocodiles nearby and when temperatures do not necessitate thermoregulation. The study suggests that gaping could be used as a form of thermoregulation and intra-species communication.

Surgical implantation of radio tags in three eel species (Anguilla spp.) in South Africa.

Studies have reported poor survival of surgically tagged freshwater fishes in warm African waters. This study aimed to assess the applicability of using radio telemetry (and surgical implantation of tags) for Anguilla spp. Nineteen yellow eels (Anguilla bengalensis, A. marmorata and A. mossambica) were surgically implanted with radio tags between October 2018 and January 2019 in the Thukela River, South Africa. Most eels were alive 6 months after tagging, and recaptured eels displayed advanced or complete healing at the incision site. Therefore, this method appears suitable for African freshwater eels.

Sexual display complexity varies non-linearly with age and predicts breeding status in greater flamingos.

The long-lived greater flamingo (Phoenicopterus roseus) is famous for performing conspicuous group displays during which adults try to acquire a new mate each year with varying success. We examined variation in the sexual display complexity (SDC) of wild flamingos aged between 4 and 37 yrs. SDC was defined as the product of richness (the number of different display movements) and versatility (the number of transitions between movements) within a 5 min behavioral sequence. In both sexes, date in the pairing season had a linear and positive effect on SDC, whereas age had a quadratic effect, with SDC increasing until about age 20yrs, and declining afterwards. SDC better explained pairing patterns than age, and positively influenced the probability of becoming a breeder. Our results thus support the idea that SDC is an honest signal of individual quality and further suggest that senescence in display could be an overlooked aspect of reproductive decline in species with no or weak pair bonding.