Friday, October 17, 2008

Do Mothers Inherently Favor Sons Over Daughters?

Apparently it is the case if the subject is a female wild horse and healthy. According to the researchers, this may go for other animals. The specific types of animals they refer to are animals with males that can mate with multiple individuals in a short period of time, hopefully resulting in multiple pregnancies.

Mothers invest more in a specific gender because of their own health conditions and potential reproduction of of their children. The mothers tend to invest more in sons because there is a the potential is higher for the sons to reproduce more and have more grandchildren for the mother.

Dr. Elissa Cameron, director of the Mammal Research Institute at the University of Pretoria in South Africa, and her colleagues studied wild horses in New Zealand. They tracked the various groups of horses, which consisted of at least one male and many female horses, via helicopter and horseback. They mainly focused on the interactions of mother and young.

Scientists learned that mothers invested more milk, contact, and protection in sons, when she was healthy. Mothers did this even if it cost them, their strenghth and weight. Mothers, who were not healthy, tended to invest more in daughters beause they are generally breed at least once.

It will be interesting to see if other mammals do the same thing for the same reasons or different reasons.


Posted by Duy Nguyen (5)


At 10:53 AM, Blogger PWH said...

Very interesting article. Its amazing how some mothers are willing to invest more of their time and energy to their sons than daughters. I think this is the case among many mothers within in a number of species to give better care to their sons because in the long run they will produce more offspring over the course of their lifetime.

-Joanne Philippeaux

At 11:43 AM, Anonymous Anonymous said...

Really neat article, if it is more advantageous for mothers to invest in sons, and if they do that when they are healthy, why is it that unhealthy mothers will invest more in their daughters?

-Cecelia Hunt

At 2:20 AM, Blogger Dan said...

I'm not surprised at all that this happens, it does make a lot of sense in a few ways. I would like to know however why mothers that are of worse health, invest more in the daughter.

~Dan Hong

At 1:02 PM, Anonymous Anonymous said...

Your explanation of why healthy female horses would favor male offspring makes sense. What I don't understand is the unhealthy mothers favoring female offspring. Why is that? Also, this study was done in the wild, do you think you would see the same results in domesticated horses?

-Jane de Verges

At 3:15 PM, Anonymous Anonymous said...

It makes perfect sense that mothers would invest more in sons who will reproduce more offsprings than her daughters. Very interesting article. Just curious to know why a sick mother would instead invest in her daughter. Why not just favor sons in both cases? Is it more costly to invest in sons than in daughters?

Hanbing Guo

At 6:26 PM, Blogger PWH said...

This article is very interesting but mother prefers son does not sound good. Can you explain more? What kind of condition is healthy or not?

So Jin Lee

At 6:59 PM, Blogger PWH said...

This article is interesting but I wonder if it is a large enough of a sample for them to make the assumptions that they did. Did the study focus on horse mothers with one male and one female foal at the same time? Why do you think it is that the mother horse would care about how many grandchildren she had?

Posted by: Lindsay Goodyear

At 7:28 PM, Blogger PWH said...

This is a very interesting article, although the last ide you mention does leave me hanging about why the unhealthier mother would treat the daughters better. I would think that they would use the same logic as the other healthier horses and feed the son more since he would eventually yield her more grandchildren.

-Helen Thi

At 7:34 PM, Anonymous Anonymous said...

This is a very interesting article. It makes me wonder how traits like this specific mothering behavior evolve. It's a little hard to put into words exactly what I'm thinking, but how did female horses "know" to evolve the behavior of favoring male offspring? To do that, the horses would have had to "know" somehow how many descendants it had, so the behavior of paying more attention to males would be favored. I'm not sure I'm coming across clearly, but does anybody else understand what I'm asking?

-Corinne Delisle

At 7:40 PM, Anonymous Allison Cornell said...

I never really thought about this happening, but it makes a lot of sense for the mother's to favor the sons. What I am very confused about is why her health status makes a difference with the amount she invests in the foal. If she was unhealthy, I would think she wouldn't be able to invest a lot with her young in general. Perhaps a daughter is more understanding and comforting to a sick mother and therefore the bond and investment is higher. I'm really not sure on this one.

~Allison Cornell (5)

At 11:20 PM, Anonymous Anonymous said...

Interesting article but in a way it kind of doesn't surprise me because there are other cases of favoritism of one sex over another in other animals. Even many humans do it to their children. Anyway, I wonder how is the interaction between a unhealthy mother and her daughter different from the interaction between a healthy mother and her son?

- Debbie Theodat

At 11:20 PM, Anonymous Anonymous said...

It's not a surprised, such as a case in many animals that mothers invest more time in males. I'm really curious at the reason behind why unhealthy mothers would invest more time to the daughter?

- David Huynh

At 11:46 PM, Anonymous Anonymous said...

Interesting, so far in class all I have heard was that in any given species of animals mothers always favors stronger offspring but I never thought that sex was also involved. It does make a lot of sense for a mother in an animal species to favor their son because of the more reproductive chances but unhealthy mother taking care of their daughter doesn’t make sense to me. I mean even if they are unhealthy wouldn’t they still take better care of males just because they breed more.
-Tenzing Y. Dundutsang

At 9:16 PM, Anonymous Anonymous said...

It seemed weird to me that a horse that wasn't as healthy would spend more time with the daughter. Is this because she doesn't have enough energy or strength to tend to the males? I wonder how it all evens out in the end, in that there are always enough healthy females for all of these strong males to mate with. This might be out there, but maybe when the weaker female takes care of her daughter, it is because she is weak and needs to replace another strong female into the population. I wonder if it is all regulated by hormones, I'm sure it is. Do you know how many times a female horse can mate in it's lifetime? If it is a larger number, then maybe by the time the mother horse is older and therefore weaker, or even just sick and weak but knows it's time is almost up, that it feels the need to replace herself with another strong female. Interesting.

Rachel Carboni

At 7:33 PM, Anonymous Anonymous said...


Unhealthy mothers tend to invest more in daughters beacuse they are unable to take the injuries when they play with their sons, injuries usually arise from this play time. I think domesticated horses tend to be different because of the situation.


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