Jennifer Colvin

Bagely et al. (2006) studied the chemosensory responses of male African elephants to the urine of female African elephants in different stages of oestrous to determine if pheromones are released in urine[1].

While Z7-12:Ac, a preovulatory pheromone, has been isolated in Asian elephant urine, no such pheromone has been found in African elephant urine for chemical signaling. In order to determine if a comparable pheromone is present in African elephants, researchers completed three trials of bioassays with a control (vanilla extract and water), with luteal urine (3 weeks prior to ovulation) and with LH2 urine (corresponds with ovulation) from seven different females. The reproductive status of each female was confirmed with blood tests when the urine samples were taken. Each male was exposed to three different samples (control, luteal from one female, and LH2 from another female) in the three trials. Multiple trials were required to determine whether the male was investigating because the urine was novel, or whether the male could distinguish between possible hormones in the urine. Chemosensory behaviors (sniff, check, place, and flehmen) and other accessory behaviors were recorded upon exposure. The researchers found that 75% of the behaviors exhibited were chemosensory, and that during trial one all samples were examined at length by the male. Over each trial period (about 1-2 hours) the samples were each examined for less time; however, there was only a significant drop in the time that luteal urine was examined between trial two and three. LH2 urine was examined less, but not significantly less over all trials, while the control examination time remained low and stable over all trials. The researchers concluded that because males spent much more time using chemoreceptors to investigate the urine collected from females during ovulation that females do release pheromones in their urine. Additionally, the male elephants generally used check, place, and flehmen to examine the samples (instead of sniff), so the researchers determined that the pheromone was not likely to be volatile.

This is consistent with the information presented in class regarding chemical signal transmission and reception. It was mentioned that many females and males release pheromones into the environment through their urine by marking or spraying. The researchers proposed that this is the method that African elephant females use to advertise what part of the estrous cycle they are in. Additionally, pheromones can either be highly volatile (disperse in air) or not volatile based on their size and structure. This is consistent with the findings because the elephants mostly employed the use of direct contact with the samples instead of simply sniffing them, suggesting that the pheromone was large and not very volatile. Finally, in class it was mentioned that the vomeronasal organ, located between the nasal cavity and the roof of the mouth, is very important in detecting pheromones. This is supported by the fact that the rate of flehmen in male African elephants was much higher for the LH2 urine (the urine that would be most likely to contain pheromones from the female). This study is important to chemical signaling research because it proposes further work that needs to be done in the field to identify specific pheromones released by African elephant females.