A Guide To Understanding Sheep Ageing

A Guide to UnderstandingSheep AgeingMaterial adapted and presented by: Andrew Walker, Msc, RPBioMinistry of Forest Lands and Natural Resource OperationsOkanaganPresentation originally developed by: Bill Jex, RPBioMinistry of Forest Lands and Natural Resource Operations- Skeena

Outline Biology of Horn GrowthProvincial RegulationsAssessing AgeExamplesRecommendations for HuntersReferencesM. Seacat

Biology of Horn GrowthA. WalkerA. Walker A horn is a pointed projection of skin onthe head of various animals Horns consist of a covering of keratin andother proteins surrounding a core of livebone. True horns are found mainly among theruminant artiodactyls in the familiesAntilocapridae (pronghorn) and Bovidae(goats, sheep, etc.). Horns start to grow soon after birth, andcontinue to grow throughout the life ofthe animal (except in pronghorns).

Annuli are formedduring winter False-annuli occurwhenever a ram’shorn growth changes There isproportionalsymmetry in thedistances betweeneach annulus Greatest growthduring the 2nd year.

True annuli formdistinct linesthrough theentire horn

Thinhorn Sheep

Bighorn Sheep

Provincial Regulations "full curl thinhorn rammountain sheep" means anythinhorn ram mountainsheep that has attained theage of 8 years as evidencedby true horn annuli asdetermined by the regionalmanager or his designate, orwhose horn tip, whenviewed squarely from theside at right angles to thesagittal plane of the skull,extends dorsally beyond thenose bridge plane;

Assessing AgeWhen considering the age of a ram there are clues to whether theram is young and possibly not legal: Large spacing between annuli near base Smooth horns especially around the bases Lots of dark horn near the base (black horn generally indicatescurrent years growth) Not full curl Not broomed Nose does not have the rounded or “roman nose” appearance Horns have little or no outward flare

Sheep horns arerarely symmetrical

Annuli can be easy todetermine, based on clear horngrowth and well definedannulor groves and annulus‘lip’.

True Annuli True annuli form a dark groove that is accentuated on theouter curve of the horn. The inter-annuli distance gets proportionally smaller afterthe second annuli. False annuli are often bulges and the grove does notextend around the back of the horn.

Examples:Ram #1

Ram #1 The annuli are notwell defined.

Ram #2 Watch for falseannuli

Ram #2 This ram has a seriesof false annuli thatwould be difficult tosee in the field Some life historycharacteristic causeshorn growth in thisram to change intraannuli

Ram #3 Look at inter-annuli distance

Ram #3 The key with this ram is to notethe growth pattern and thedistinctive ‘lip’ formed at eachtrue annulus.

RamRam#4#4This ram has a very tight curl, making the visibilityThe tightcurlmakesof thelaterannuli aageingthis ramdifficult.challenge.We canaccurately estimatethe age though if we use the clues in thehorn; again, while rams on averagehabitat have slower growth and shorterinter-annulus distances, rams on goodhabitat can have more uniform growthand more consistent inter-annulusdistances.so, how old is this ram?

Ram #4 The tight curl hides thebase, but note that theinter-annulus distanceremains consistent, onlygetting progressivelyshorter with age. Clearly defined annuli. This ram is at least 9 yearsold.

Ram #5

Ram #5 This ram can beaccurately aged at 10years old based on theformation of an annulus‘lip’ and the interannulus spacing.

Ram #5 This shows the 10th annulus. Also, the double-groove pattern canbe seen in the 7th and 9th annuli aswell, lending more proof that thisram should be aged at 10 years old.

Ram #6 Watch for falseannuli.

Ram #6 False annulidon’t have adistinct grove orannulus ‘lip’.

Recommendations: Get the best optics, that you can afford.Get as close as possible.Take your time and be patient.Get as many angles and profiles of the horns as possible.Be confident in your decision.A. Walker

Additional ReferencesMountain sheep of North America. Edited by R. Valdezand P.R. Krausman. The University of Arizona Press, Tucson, Arizona, USA.BC Hunting ing-stones-sheep-in-the-field/BC Hunting Regulations ing/regulations/Wild Sheep Society of ml

False-annuli occur whenever a ram’s horn growth changes such as during a seasonal migration between ranges or when an inju對ry occurs. . When considering the age of a ram there are clues to whether the ram is young and possibly not legal: . there are clues that might lead one to believe the ram may b對e a young ram vs an older, mature .