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well, I'd assume if they eat less because there is less to eat then the lamb will not grow that much bigger...

That is not what scientific studies show. The females body is geared to allow her young to get the best possible opportunity to survive. She will use all her resources to give it the best possible chance. At the point where things become critical, she will either abort the baby or die herself.

Also take in to account that it is seldom that things get really critical. These animals are superbly adapted for their environment.

What we have here is a typical situation of where a piece of "knowledge" gets repeated time after time, and then becomes accepted as "the truth." Which it isn't.

well, I guess you're right then...I wasn't sure myself, that's why I asked

And that is one of the things wrong with the internet, and with a site like Wikipedia. Because everybody "knows" this to be true, it is accepted when it is posted, and not corrected. And the myth is perpetuated.

So we can say 100% it is just a legend it can not happen

Just remember that there's a difference between "variance" and "being able to hold back." Smithers says the gestation period is 194-200 days. Now, as with humans, you're going to get some that are slightly out of that range. Some will drop a bit sooner, and some a day or so later. That's not to say that they're planning that and doing it on purpose - it's just the say things are. Stress, drought, etc. - there are factors that may cause earlier drop and even abortion. But holding back...

Just to clarify...

The earlier posts about impala still being pregnant after rains has nothing to do with the "holding back" theory...

Two separate issues!

I still believe they can hold back a few hours if the danger to the little ones is close, but just my personal opinion.

Another fact is that a herd of females will drop their calves almost simultaneously, given a day or two!

And once again, this is not only confined to Impala!

Not an Impala expert by any stretch of the imagination but could that not be because female animals that live together tend to come into oestrus together, I know that most domestic animals do and so do humans, this is why flocks of sheep all lamb together.

I have no idea if it is true but I also believe that a female giving birth causes other females to go into labour. I believe it could be a hormone indiced reaction as a female in labour and soon after birth will have a surge of the hormone oxytosin (this helps her to bond with the newborn), now when I worked on a comercial pig unit this was the same hormone we used to induce labour in the sows.......

If anyone knows better please feel free to correct me

Long time no see, sammylou!

Yes, groups of women sharing accommodation over an extended period do indeed start synchronising their fertility windows due to pheromones released into the air!

Amazing, and very good points!

I agree with that explanation.

But I wonder, in a natural situation, which female decides to go "first", so to speak...

Fascinating!

Yeah been far too long Richpins - it's good to be back though

It would be interesting to find out if there has been any research done as to which female gives birth first, I suppose it could be the most dominant females first, or the least dominant (which would make sense as any predators in the area may well kill the offspring of the 'lower' female first giving the more dominant females a better chance initially). Or of course it could always just be random..........

Would make an interesting research project for a student if it hasn't been done before (right I just need to find a degree that would mean I could do that as my dissertation )

I think it would be random, as the lamb will not first ask "is my mom dominant and has the others been born yet".

Holding back? I know that in roe (ree wild) after conception, a fetus not immediately starts to develop but can hold back for 1 or 2 months....

My question on this topic is...

Late last year the Impala in the south of the park had given birth already and in the north they were still carrying. After the first proper rains in the north the Impala all gave birth, this was more than a month later than their cousins in the south. Now did the ones in the north mate more than a month later than the ones in the south, did they know at that stage that the rains would be later in this area?

I still think that they will hold out a certain amount of time for the rains to come.