Ages and Reproductive Cycles in a Male Gray Squirrel Population

Kirkpatrick, Charles M.; Hoffman, Roger A.

doi:10.2307/3796750

Cited by 19 publications

(17 citation statements)

References 6 publications

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“…2,3 Male EGS normally undergo a semiannual cycle of testicular recrudescence and regression and occasionally skip entire breeding seasons. 11,24,25 Although some animals in this study may have been experiencing a cessation of reproduction, there was no evidence of gonadal inactivity in any control males. The extremely reduced testes weights, epididymal diameter, and atrophy of the prostatic glandular lumen in the vaccinated males were absent from the controls.…”

Section: Discussionmentioning

confidence: 66%

Immunocontraception in Eastern Gray Squirrels (Sciurus carolinensis): Morphologic Changes in Reproductive Organs

Pai¹,

Bruner²,

Schlafer³

et al. 2011

Journal of Zoo and Wildlife Medicine

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Eastern gray squirrels (EGS) (Sciurus carolinensis) damage trees through bark stripping or gnawing due to territorial marking or agonistic gnawing behavior in concert with higher densities. This study was conducted to determine the effects of a contraceptive vaccine on EGS and its reproductive organ histology. Free-ranging urban EGS were vaccinated with the immunocontraceptive GonaCon. All EGS were > or = 6 mo of age as determined by a combination of pelage characteristics and body weights. The vaccine was administered by injection at a dosage rate of 0.4 ml containing 400 microg of GnRH-mollusk protein conjugate i.m. in the thigh to 33 EGS (17 male [m], 16 female [f]) in trapping session 1 (TS1), 23 (14 m, 9 f) in trapping session 2 (TS2), and 11 (8 m, 3 f) in trapping session 3 (TS3). A sham injection containing 0.4 ml saline-AdjuVac was given as control to 22 EGS (16 m, 6 f) in TS1, 20 (12 m, 8 f) in TS2, and 8 (4 m, 4 f) in TS3. In the last trapping session (TS4), 35 EGS (16 treated, 19 control) were killed for necropsy to evaluate histologic changes in testes and ovaries. Treated EGS males had testicular, prostatic, and epididymal atrophy compared with control EGS males. The tubuli seminiferi and prostatic glandular lumen of treated EGS males were atrophic, and the epididymal lumen contained no sperm cells. No histologic changes were observed in treated EGS females; however, females likely were not collected when changes due to GonaCon would have been observed. There were no observable histologic differences in the pituitary gland of treated and control EGS. There were no statistically significant differences in either testosterone or progesterone concentrations between control and treated EGS. Although there were no serious side effects to the vaccine, six EGS developed injection site abscesses. GonaCon may be a potential tool for EGS population control.

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Section: Discussionmentioning

confidence: 66%

Immunocontraception in Eastern Gray Squirrels (Sciurus carolinensis): Morphologic Changes in Reproductive Organs

Pai¹,

Bruner²,

Schlafer³

et al. 2011

Journal of Zoo and Wildlife Medicine

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“…The state of sexual development is difficult to ascertain purely from external examination. It has been demonstrated (Kirkpatrick & Hoffman, 1960) that fecundity cannot be determined with accuracy from the external condition of the animal. However, certain features can indicate the probable state of development of the testes, for example, the scrotum increases in size, loses its fur and develops a black pigment as the squirrel becomes sexually mature.…”

Section: Resultsmentioning

confidence: 99%

Seasonal changes in the testis and epididymis of the American Grey squirrel, Sciurus carolinensis

Pudney

1976

Journal of Zoology

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The histological changes in the testis and epididymis of the American Grey squirrel, Sciurus carolinensis (Gmelin) during development and the testicular cycle are described. It was observed that male Grey squirrels, as a population, did not undergo a pronounced seasonal reproductive cycle, however, individual males did experience periods of reproductive inactivity which were asynchronous and not related to seasonal changes in the environment. It is suggested that the individual sexual cycles are due to an endogenous rhythm of gonadotrophin secretion by the pituitaries of these animals.

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“…In the U S A . regressed males were found in almost all months of the year and sexually developed animals were found in all months except by Kirkpatrick & Hoffman (1960), who found them to be absent in September.…”

Section: Discussionmentioning

confidence: 96%

“…Most males were found to regress around August and some in the period around March (Brown & Yeager, 1945 ;Mossman, Hoffman & Kirkpatrick, 1955 (Allen, 1952). The only reported exception appears to be that of Kirkpatrick & Hoffman (1960) who found no sexually developed male Grey squirrels amongst 16 examined in September, and that the proportion of sexually functional adults was much lower in July and August, as well as October and November, than at other times of the year. This paper presents data which show that male Grey squirrels in Britain exhibit a definite, locally synchronized, seasonal cycle of sexual regression and recrudescence.…”

Section: Introductionmentioning

confidence: 90%

Male Grey squirrel (Sciurus carolinensis) reproductive cycles in Britain

Dubock

1979

Journal of Zoology

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A synchronized seasonal cycle of sexual regression and development is described for the male Grey squirrel in Britain. Sexual development is maximal in December and May and minimal in August. The seasonal cycle can be overriden, but this is exceptional. Comparisons with previous work and the suggestion that the synchronized seasonal sexual cycle is general for Grey squirrels in Britain, and probably America, are made.

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Ages and Reproductive Cycles in a Male Gray Squirrel Population

Cited by 19 publications

References 6 publications

Immunocontraception in Eastern Gray Squirrels (Sciurus carolinensis): Morphologic Changes in Reproductive Organs

Immunocontraception in Eastern Gray Squirrels (Sciurus carolinensis): Morphologic Changes in Reproductive Organs

Seasonal changes in the testis and epididymis of the American Grey squirrel, Sciurus carolinensis

Male Grey squirrel (Sciurus carolinensis) reproductive cycles in Britain

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