( CNN ) -- Can you think of one sport where men and women compete against each other as equals ? Stumped ? Try horse racing , where female jockeys regularly jump in the hot seat alongside their male counterparts . But it 's not just the riders facing-off as they thunder down the track . The horses carrying them towards the finish line are locked in their own battle of the sexes -- and it seems the animal kingdom is n't as different to humans as you might imagine . While male and female thoroughbreds are fairly evenly matched in physical ability , the girls must overcome commercial and even psychological constraints to get ahead in the sporting world . Sound familiar ? `` At the top level , it does take a special filly to beat the boys , '' Paul Rogers , spokesman at the British Horse Racing Authority , told CNN . A man 's world ? It may seem like quite a stretch comparing women in the workplace to fillies in the field , but just like that so called boardroom glass ceiling , female horses are the minority in the racing world . Male horses -- known as stallions , geldings or colts depending on whether their manhood is still intact -- far outnumber females -- called fillies -- on the track . In British flat racing , 63 % of horses are male , while 37 % are female . It 's a similar story for the overwhelming number of male winners -- 67 % compared to just 33 % for the girls . Even in America 's most prestigious horse race -- the Kentucky Derby -- only three fillies have won in the competition 's 138-year-history . Hormonal horses . So why do boy horses rule the roost ? `` It tends to be that male horses are a bit bigger and taller than females -- a bit like men and women , '' said Rogers . `` A lot of it also has to do with hormones . Temperament-wise , female horses are probably a bit more placid . And when they come into season -- have their periods -- they can be unpredictable . '' That said , stallions -- male horses which have n't been castrated -- can also be flighty , if somewhat more aggressive on the track , added Rogers . Even playing field ? Yet compare their ability ratings -- zero for a dud to 140 for an unbeaten thoroughbred in the UK -- and both genders score around the same . Males have a median rating of 69 , while females score 64 . `` While size plays a role -- taller horses tend to have a longer stride -- I would n't necessarily say male horses have more stamina , '' said Rogers . `` In terms of distance , they 're probably equally adept . It 's more a question of parentage -- if mum and dad are sprinters , then their son or daughter will be the same . '' The slight discrepancy in ratings , means male horses will often carry a few extra pounds in weights , to even out the playing field . Bred for success . The high number of male race horses may also be down to their profitability off the track . `` From a racing industry perspective , if a male horse is successful on the racetrack , they will also be worth a lot more money as a breeding stud -- anything up to around $ 150,000 per offspring , '' said Tim Whitaker , head of postgraduate study in equine science at Britain 's Duchy College . `` With a mare however , she will only be able to produce one foal a year . But if you get it right -- and it is rare -- you could have a breeding stallion which earns millions . '' Perhaps the best example of a super stud 's earning power is British colt Frankel , which retired last year with an unbeaten 14-win record . Today , he commands a fee of $ 190,000 for each offspring and is expected to generate a staggering $ 150 million in his stud career . Leading ladies . That said , one of the most remarkable champions the racing world has ever seen also retired last year -- a female thoroughbred called Black Caviar . The Australian mare notched up 25 consecutive wins , becoming not just a national sports star but a celebrity who even graced the cover of Vogue magazine . `` Her allegiance level is phenomenal , '' Colin Madden , one of Black Caviar 's eight owners , said . `` She 's a powerful horse who just fronts up every time and people really like that consistency . '' The girls may have some way to go in catching the boys . But it seems that even in the equine world , the race is far from over .
Horse racing rare sport where males and females compete against each other . Not just jockeys -- but horses . Comment: More winning male horses than females , seen as taller , stronger , faster . Aussie champion Black Caviar , best female thoroughbred in history .