Clicking knees are antelopes' way of saying 'back off'

November 03, 2008

Knee clicking can establish mating rights among antelopes. A study of eland antelopes, published in the open access journal BMC Biology, has uncovered the dominance displays used by males to settle disputes over access to fertile females, without resorting to genuine violence.

Jakob Bro-Jørgensen from the Zoological Society of London and Torben Dabelsteen from the University of Copenhagen studied antelopes within a 400km2 area of Kenya. They found that the males (bulls) use a selection of signals to make competitors aware of their fighting ability, based on three different factors, body size, age and aggression. According to Bro-Jørgensen, "Rivals often use signals to broadcast their fighting ability and thereby settle conflicts without incurring the high costs associated with actual fighting".

As well as the knee clicks, which are shown to be a reliable indicator of body size, the researchers found that the size of a bull's dewlap is related to age. The authors said, "Age is a good proxy for fighting experience and may also demonstrate that a bull has 'nothing to lose' and will therefore be a more risk-prone and dangerous adversary". Finally, hair darkness reflects yet another underlying variable, most likely androgen-related aggressiveness. All of these indicators serve the useful purpose of facilitating assessment by a bull's rivals and avoiding wasteful conflict.

The antelopes' knee clicks, which can be heard several hundred metres away, are thought to be produced by a tendon slipping over one of the leg bones and, according to the authors, this can explain why they correlate with body size, "The tendon in this case behaves like a string being plucked, and the frequency of the sound from a string correlates negatively with both its length and diameter. Thus, most importantly, depth of the sound is predicted to increase with skeletal measures".
-end-
Notes to Editors

1. Knee-clicks and visual traits indicate fighting ability in eland antelopes: multiple messages and back-up signals
Jakob Bro-Jørgensen and Torben Dabelsteen
BMC Biology (in press)

During embargo, article available here: http://www.biomedcentral.com/imedia/6157235952079075_article.pdf?random=973582

After the embargo, article available at journal website: http://www.biomedcentral.com/bmcbiol/

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

Article citation and URL available on request at press@biomedcentral.com on the day of publication

2. Images of the antelopes are available here:

http://www.biomedcentral.com/graphics/email/images/general/Youngelandbull.jpg
http://www.biomedcentral.com/graphics/email/images/general/oldelandbull.jpg
http://www.biomedcentral.com/graphics/email/images/general/Elandbull1.jpg
http://www.biomedcentral.com/graphics/email/images/general/Elandbull2.jpg
http://www.biomedcentral.com/graphics/email/images/general/Elandbulltwofemales.jpg
http://www.biomedcentral.com/graphics/email/images/general/Elandhigh-jumping.jpg

3. BMC Biology - the flagship biology journal of the BMC series - publishes open access research and methodology articles of special importance and broad interest in any area of biology and biomedical sciences. BMC Biology (ISSN 1741-7007) is covered by PubMed, MEDLINE, BIOSIS, CAS, Scopus, EMBASE, Zoological Record, Thomson Scientific (ISI) and Google Scholar. The journal has an Impact Factor of 5.06.

4. BioMed Central (http://www.biomedcentral.com/) is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.

BioMed Central

Related Body Size Articles from Brightsurf:

Body size of the extinct Megalodon indeed off the charts in the shark world
A new study shows that the body size of the iconic gigantic or megatooth shark, about 15 meters (50 feet) in length, is indeed anomalously large compared to body sizes of its relatives.

Weight gainers more likely to underestimate their true body size
People with obesity who gain weight have a tendency to perceive their own body size as smaller than it actually is compared to those who maintain a stable weight, according to new research following more than 2,000 people with obesity from the Swedish Obese Subjects (SOS) study over 10 years.

Whole body ownership is not just the sum of each part of the body
Differences between whole body and body part ownership were clarified using scrambled body stimulation in a virtual environment, wherein the observer's hands and feet were presented in randomized spatial arrangements.

'Like a video game with health points,' energy budgets explain evolutionary body size
Budgeting resources isn't just a problem for humans preparing a holiday dinner, or squirrels storing up nuts for the winter.

Lifestyle coaching proves effective in decreasing body fat and waist size
Losing weight during and after menopause is not easy, but it's not impossible, either.

Short-term study suggests vegan diet can boost gut microbes related to body weight, body composition and blood sugar control
New research presented at this year's Annual Meeting of the European Association for the Study of Diabetes (EASD) in Barcelona, Spain (Sept.

Waist size, not body mass index, may be more predictive of coronary artery disease
For years, women have been told that weight gain could lead to heart disease.

Memory research: Fruit flies learn their body size once for an entire lifetime
Drosophila melanogaster develops stable long-term memory for its body size and reach through motion parallax while walking.

Size matters: New data reveals cell size sparks genome awakening in embryos
Transitions are a hallmark of life, and so there is a transition during early development when an embryo undergoes biochemical changes, switching from being controlled by maternal molecules to being governed by its own genome.

Size is everything
The susceptibility of ecosystems to disruption depends on a lot of factors that can't all be grasped.

Read More: Body Size News and Body Size Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.