Stories and thoughts about small animal reproduction and ultrasound

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Radioprotection in the veterinary practice

On Sunday January 31st, I was invited to give a short lecture about radioprotection in the veterinary practice.

Ionizing radiation is not a new or unknown field for me, as I was a member of Greek Airforce’s NBC (Nuclear, Biological, Chemical) Medical Response Team from 1998 to 2007. Apart from that, the effects of any type of radiation on the reproduction system and on the fetus are also of great importance for me because of my special interest in small animal’s reproduction. One of my latest research project has to do with the potential effects of specific types of electromagnetic radiation in pregnant rats.

So those of you that might find something interesting in my presentation, you can read the attached pdfs! One in Greek and one translated in English!

Have a nice week!

Radioprotection and the role of the vet-Greek

Radioprotection and the role of the vet-Engl



Twitter and reproduction of rodents. Part 2.

Time has come for the 2nd part…


Chinchillas become sexually mature at an average age of 8 months: females 8.5 months (2-14), and males at 8 (4-12) months.

They are polyestric animals.  Females cycle seasonally (November to May in northern hemisphere). They come in estrus every 28-35 days. They also present postpartum estrus: 12 hours after parturition! Estrus lasts 3-4 days, perineum becomes reddened, the normally tightly closed vagina opens and expels a wax-like plug. Vulval swelling is not present.

Mating occurs biannually. Chinchillas form monogamous pairs or can be kept in harems. Gestation lasts 111-128 days. Pregnancy can be detected by palpation at 90 days. Litters size is 2 (1-6). Parturition occurs early in the morning. Newborns are fully furred and have their eyes open. They weigh 30-50 gr. Weaning occurs at 6-8 weeks, but they are able to eat solid food quite early (from the 1st week) as they are born with teeth!




Female rats are polyestric animals and they come in estrus every 4-5 days.

Social groups of rats are often formed of multiple males and multiple females. One male is dominant and a linear male hierarchy may form. The species is polygynous, and the dominant male is the most successful breeder. Territories and mates are defended through aggressive behavior.

Rats are able to breed throughout the year if conditions allow. The peak breeding seasons are summer and autumn. Females can produce up to 5 litters in one year. The gestation period ranges between 21 and 29 days, and young rats are able to reproduce within 3 to 5 months of their birth. Babies are born with closed eyes and hairless. Weaning occurs at 3 to 4 weeks of age.


Pregnancy diagnosis of the rat at the 8th day (Image by George Mantziaras)


Heart rate estimation of a rat fetus at the 12th day of pregnancy (Image by George Mantziaras) 


Ultrasound of a rat fetus on the 18th day of pregnancy (Image by George Mantziaras)




Breeding onset is at about 50 days of age in both females and males. Mice are polyestrous and breed year round. They are spontaneous ovulators. The duration of the estrous cycle is 4–5 days and estrus lasts about 12 hours. Vaginal smears can be used to determine the stage of the estrous cycle. Mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a vaginal smear is also a reliable indicator of mating.

Female mice housed together tend to go into anestrus and do not cycle. If exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours.

The average gestation period is 20 days. A fertile postpartum estrus occurs 14–24 hours following parturition, and simultaneous lactation and gestation prolongs gestation 3–10 days owing to delayed implantation. The average litter size is 10–12. Inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weigh 0.5–1.5 g , are hairless, and have closed eyelids and ears.They are weaned at 3 weeks of age.




Gerbils reach sexual maturity at 10 to 16 weeks. They are polyestrous and they cycle every 4-7 days. They form monogamous pairs.

Gerbils will mate for several hours, in frequent short bursts followed by short chases, when the female allows the male to catch her. Once he catches her, the female will squeak and make flick motions to get the male off her. Males will not attack females except in rare circumstances, which may also include them having been separated from their original mates, or widowed. A female may attack a male, but usually he is more than a match for her. Copulatory plugs form in the reproductive tracts of females that hinder subsequent matings. The presence of these copulatory plugs suggests a polygynandrous mating syste

Gerbils may also experience postpartum estrus and delayed implantation, such that a new litter begins developing as soon as the first is weaned. Gestation periods, if females are not lactating, last 3 to 4 weeks, longer if lactating. Overall, litter sizes range from 1 to 13, although litters of 4 to 7 are much more common. Young gerbils are born completely naked and blind. Eyes open about two or three weeks after birth. The young can walk quickly and hop about on all fours at about three weeks. At around one month of age, the young are weaned and independent.




Hamsters reach puberty at the age of 6-8 weeks. They present estrus every 4 days.

Hamsters, as cricetines,  are promiscuous, with males and females both having multiple mates. During mating, a copulatory plug forms and seals the female’s reproductive tract, preventing subsequent males from successfully fertilizing the female’s eggs. A female hamster often drives a male out of her territory soon after mating.

Cricetines are seasonal breeders that mate and raise their litters from February to November. Females bear 2 – 4 litters per year. Gestation is short, lasting 15 to 22 days, and litter sizes average 5 to 7 (1-13). Young hamsters nurse for about three weeks, and are sexually mature at six to eight weeks.


That’s all for rodents’ repro for the moment. I’m not sure if there will be a 3rd part. Maybe yes, if you ask for that!

Thanks for reading,

Bye bye till the next time!


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Twitter and reproduction of rodents. Part 1.

Happy new year!

Time for the first post of 2016!

Last week (back in 2015) I was asked via tweeter ” How do female porcupines give birth?”. My first thought was “very very very carefully”! Later, with the help of doctor Google, I found some interesting information at an excellent post by Dr. Quinn Shurtliff.

But, if we just remember that porcupines are rodents, we will realize how many differences they do have when compared to other rodents, such as beavers, rabbits, rats, mice etc etc etc!

So in the next paragraphs we will try to sum up the most important -and maybe funny- facts about reproductive physiology of the rodents.

Let’s begin with the big ones…



Female porcupines are solitary animals except during the breeding season, which begins during the fall. Females may be polyestrous and re-cycle in 25 to 30 days if fertilization does not occur at the time of ovulation. Ovulation is spontaneous and may alternate between the left and right ovaries. The female porcupine is in heat for 8-12 hours. The testes of male porcupines descend into scrotal pouches during late August and early September. Spermatogenesis reaches its highest level during October.

When breeding season begins, females secrete a thick mucus which mixes with their urine. The resulting odor attracts males which fight for receptive females. They use loud vocalizations, violent biting, and each uses his quills as weapons. Although the competition happens in trees, mating exclusively happens on the ground. Once a dominant male is successful, he approaches the female and uses a spray of his urine on the female. Only a few drops touch the female, but the chemical reaction allows the female to fully enter estrus. When porcupines are mating, they tighten their skin and hold their quills flat, so as not to injure each other. Mating may occur repeatedly until the female loses interest and climbs back in to the tree. After mating, a copulation plug is formed.

The North American porcupine has a long gestation period when compared to other rodents. Pregnancy lasts 210 (205-217) days with the young being born from April to June. Porcupines give birth to a single young. At birth, they weigh about 450 g, which increases to nearly 1 kg after the first two weeks. They do not gain full adult weight until the end of the second summer about 4.5 kg. Offspring are precocial with open eyes when born. Senses of smell and hearing develop as the young grow. The quills of young porcupines are soft at birth but harden within one hour. Parental care is provided by the mother. Mothers remain with their young for up to six months. Youngs are not sexual mature until the age of 25 months for females, and 29 months for males.




Beavers are monogamous animals! The breeding season begins in January and February in both American and Eurasian beavers. Estrus lasts 10-12, maximum 24 hours. Copulation most commonly takes place in the water and in some cases can take place in the lodge. The male will approach a female floating in the water from the side and copulation may last from 30 seconds to 3 minutes! Most copulations occur at night. If not fertilized, female beaver may come into estrus again two weeks later.

The female is sexually active after 1.5 to 2.5 years old. Most beavers do not reproduce until they are three years, but about 20% of two-year-old females reproduce. Pregnancy of the American beaver lasts around 107 days and of the Eurasian 60-128 days. The average size litter is 3 to 4 young  (1-4) for the American and 1 to 3 (2-6) for the Eurasian beaver.

Baby beavers or “kits” are born well-developed, with open eyes and ample body fur. Newborn weight is 230 to 630 g. They are comfortable with the water in the span of a single day post-birth, and can even swim.



In fact rabbits ARE NOT RODENTS! They were considered to be but not anymore! They are lagomorphs. Nevertheless, we will demonstrate some things about them in the following paragraphs:

Rabbits are well-known for their reproductive capacity! Mating in rabbits is generally polygynandrous (=a reproductive strategy that occurs when two or more males have an exclusive sexual relationship with two or more females. The numbers of males and females need not be equal.), though males will attempt to monopolize particular females. Forget monogamy in this case…

Sex determination is difficult and easier with puberty (4-9 months). Small breeds mature earlier than larger breeds (body weight is more important than age). Also does (females) mature earlier than do bucks (males, that achieve optimum sperm production 40-70 days after puberty).

Does are induced ovulators with no defined estrous cycle, although a cyclic rhythm in sexual receptivity exists (can show swollen vulva). Females experience postpartum estrus and thus may have several litters per year (maybe more than 400 per year), though spontaneous abortions and resorption of embryos are common. Also they can be lactating during pregnancy.

During copulation bucks rapidly mount receptive females, reflex ejaculation follows immediately on intromission and copulatory thrust is so vigorous that buck falls backward or sideways and may emit a characteristic cry!

Gestation length is 30-32 days, and the average litter contains 5 to 8 young. Rabbit placenta allow an unusually high degree of contact between maternal and fetal bloodstreams, a condition they share with humans. Parturition occurs usually in the morning and lasts less than 30 minutes.

Neonates, called kittens, are blind, without hair and helpless, they weigh 50 g, their ears are functional from day 7 and their eyes open on day 10. They do not require stimulation to urinate! The mother visits the nest for only a few minutes each day to nurse them, but the milk is extremely rich. Young are weaned at 5 weeks of age and can live up to nine years. Males are not involved in caring for young. Mortality rate in the first year of life is very high, sometimes more than 90%.

Guinea pigs


Guinea pigs no longer exist in the wild, therefore, mating systems in natural environments are unknown. In domestic populations, mating is heavily influenced by humans. Both monogamous and polygamous systems occur, depending on how animals are housed.

Prior to mating, males smell a potential mate’s genital area and scent mark their mates with urine. Males are very protective of their mates, particularly when multiple males are housed with a single female.

Male guinea pigs reach sexual maturity at about 3 months while females earlier at about 2 months of age. Estrus occurs 3 to 4 times per year and lasts approximately 16 days. Females are polyestric animals as they cycle every 15-17 days. They are spontaneous ovulators and estrus lasts 6-11 hours.

Mating and fertilization usually occur at night, within 20 hours of ovulation. A solid mass of coagulated ejaculate (plug) that falls out of vagina several hours after mating and confirms copulation; hard and waxy product of male secretions. Guinea pigs do not exhibit seasonal mating patterns in domestic populations.

Gestation lasts 69 days (59-72). The average age at first pregnancy is 175 days. It’s important to breed females at a young age, ideally at about 6-12 weeks old (400-600 g body weight) and definitely before 6-8 months old; after 8 months old the pubic symphysis fuses and dystocia will occur. The average litter size is 3 pups (1-13). Parturition is typically rapid with only a few minutes between births. Females do not built nests, but they express fertile postpartum estrus 2-10 hours after parturition!

Newborns are called pups or young (but not piglets) and they are precocious (fully furred, eyes open). Urination and defecation must be stimulated. Birth weight is 45-115 g. Lactation lasts 3 weeks, sows are not very “motherly” and weaning occurs 14 to 21 days after birth.

Enough…more to come on part 2!

Until then, I wish you all health and happiness!

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Earth’s Top 10 Weirdest Animals, Part 1

Wander Woman Thea

Our beautiful Blue Planet is home to a staggering variety of life that ranges from the simplest, single-celled amoeba to the most complex and advanced mammals. We interact with a variety of these species on a daily basis, whether its swatting away an annoying fly, taking your dog for a run or giving your husband a pat on the back for being civil to your mom, even when she chews him out for not being Brad Pitt.

Then of course there are those species we only get to see on the odd occasion – perhaps at the zoo, on safari or even in your own backyard if you’re lucky (or unlucky depending on your worldview). Bears, raccoons, porcupines, deer, wild cats, monkeys… the world is full of places where human and beast regularly brush shoulders with each other. Unfortunately, it’s rarely for the good of the beast or for your…

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Earth’s Top 10 Weirdest Animals, PART 2

Wander Woman Thea

Welcome to the second installment of this two-part blog series on animals you’d likely encounter in a Ripley’s Believe It Or Not zoo if the Ripley’s Believe It Or Not franchise did indeed have a zoo. If you haven’t read Part 1 you can check it out by clicking the following link:

Read Part 1. I mean, who reads Part 2 before reading Part 1? Are you dyslexic? Are you an anarchist trying to upset world order? Or are you another hipster on yet another fruitless quest for originality?

Just kidding.

Here are the next 5 super strange critters on my list!

Deep Sea Pompeii Worm

Alvinella pompejana 

Deep sea pompeii worm

Image Source:

Contrary to appearances, this is not some outlandish proctology case study. It’s a very special kind of deep-sea worm that belongs in the cool-sounding category of the “extremophiles,” which are organisms that thrive in extreme environments. The neighborhoods…

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Stories from Milan and thoughts about canine prostatic neoplasia…

One more time at Milan University! The Vet School still sitting there, full of veterinary histories as it was firstly established in 1791!  And always full of memories for me as I visited it for the first time back in 2004 in order to attend the 3rd ESAVS course of small animal reproduction. From that time till now a fruitful cooperation between the Clinic of Obstetrics & Gynecology and myself began…

Our latest research project is focused on the prostate of the dog. It may sound boring but it is not! Though the prostate is a well-studied gland, a lot of things have to be made clear yet. For example, a lot of discussion between breeders, dog owners and vets has been observed all these years, concerning the prevention of cancer of the canine prostate. Some claim that castration prevents cancer development while others don’t want to hear about it!  But the real question is “how common is neoplasia of the prostate of the dog?”. The correct answer to this could be something like “It depends”! In the following lines I will try to explain why.

During the 90’s and early 00’s it was believed that intact (= not castrated) male dogs have a high probability to develop prostatic neoplasia. So the common preventive practice was castration (orchiectomy in other words) which was performed at a very young age, even before puberty in some cases! Castration of course has some other strong benefits, such as prevention of development prostatic benign hyperplasia, prostatic cysts and other pathologies of the gland. Without a doubt castration is also a great “tool” for the control of stray dog population, that has to be combined with education of the owners.

These advantages are all true. Except one: prevention of neoplasia! In the (not so) recent literature it is well demonstrated that “neutered males had a significantly increased risk for each form of prostatic cancer. Neutered males had an odds ratio of 3.56 for urinary bladder transitional cell carcinoma (TCC), 8.00 for prostate TCC, 2.12 for prostate adenocarcinoma, 3.86 for prostate carcinoma, and 2.84 for all prostate cancers.”(Bryan et al, Prostate, 2007).

And of one the Guru’s of small animal reproduction, Michelle Kutzler, makes things clear enough: “Not only does castration not protect against future development of prostatic neoplasia in dogs, but incidence of prostatic neoplasia is higher in castrated dogs” (Neoplasms of the Prostate in Small Animals, The Merck Veterinary Manual, 2013).

These infos also reflect my own feeling, deriving from my almost 20 years’ small animal practice experiences. The “true” and “real” cases of prostatic neoplasia that I have seen are less than 5 (3 as far as I remember). “True” and “real” mean “proven” by histologic or cytological examination of prostatic samples taken with biopsy or fine needle aspiration (FNA). On the other hand, diseases such as benign prostatic hyperplasia, cysts, prostatitis (= inflammation of the prostate gland) are almost everyday practice to my experience…

But in several congresses and several discussions with vets from other countries, I realize that scientific community is really worried about prostatic neoplasia prevention and treatment! How can it be??? Am I missing cases? Or maybe vets from other countries are overestimating the frequency of prostatic neoplasia development? Well, none of these…it’s a matter of …let’s say… “culture”! And I will explain you what I mean: In countries of the southern Europe such as Greece or Italy, castration of the male dogs is not so familiar as in other countries such as Great Britain, USA, Belgium and maybe France. Castration is mostly performed in cases of prostatic disease (for example benign prostatic hyperplasia or prostatic cysts), very very rarely in young dogs and almost never in dogs before reaching puberty! As a result the incidence of prostatic cancer is low!

So when we are studying or discussing the epidemiology of prostatic diseases we also have to consider the possible differences between countries.

Also we have to keep in mind that early castration (despite what was common belief) increases the risk of development prostatic neoplasia! But on the other hand has many many many advantages – that will be fully discussed in the near future! In any case, your vet knows the pros and cons and always decides the best for your dog, depending the problem, the current health status, the age etc etc etc!

Merry Christmas to all!

Keep in touch!