Mounting Behaviors (Hormonal)

Mounting behavior in guinea pigs is a natural component of their social and reproductive repertoire, but when driven by hormonal excess or imbalance it can become persistent, disruptive, and indicative of underlying health concerns. In its normal context, mounting serves two distinct functions: reproductive mating behavior and social dominance signaling within group hierarchies. Hormonally driven mounting becomes a health and welfare concern when it occurs with excessive frequency, causes physical injury to the mounted animal, produces chronic stress within a social group, or reflects pathological endocrine conditions such as ovarian cysts or adrenal disease. Understanding the hormonal mechanisms behind mounting is essential for distinguishing normal social behavior from behavior that requires veterinary evaluation and intervention.

Guinea pigs are highly social animals with complex group dynamics governed in part by hormonal signaling. In intact males, testosterone drives both reproductive mounting directed at females and dominance-related mounting directed at other males as part of hierarchy establishment. In females, estrogen fluctuations during the estrous cycle influence receptivity and can trigger mounting behavior directed at cage mates of either sex, particularly around estrus. The guinea pig estrous cycle is approximately 15 to 17 days in length, and behavioral changes including mounting activity typically concentrate around the one to two day estrus period when estrogen peaks and the female becomes receptive to mating. This cyclical pattern helps distinguish normal estrous-related behavior from pathological hormonal excess.

The distinction between normal and pathological mounting behavior lies in frequency, intensity, context, and associated signs. Normal dominance mounting in a stable group occurs intermittently, is relatively brief, does not cause injury, and subsides once hierarchical positions are established. Normal reproductive mounting in intact males housed with females follows recognizable courtship patterns including rumblestrutting, circling, and purring vocalizations before the mount attempt. Pathological mounting, by contrast, is characterized by relentless persistence that does not respond to social cues from the mounted animal, occurs outside of expected contexts such as a neutered male mounting obsessively, escalates in intensity over time, or is accompanied by other signs of hormonal disturbance such as hair loss, aggression, or physical changes. Recognizing this distinction helps owners determine when mounting warrants veterinary attention.

Hormonal mounting behavior has direct welfare implications for both the mounting animal and its cage mates. The mounted animal may experience chronic stress from repeated unwanted advances, physical injuries including hair loss from grasping, skin abrasions, and bite wounds when mating attempts meet resistance. Persistent mounting disrupts normal social bonds within the group, interfering with resting, feeding, and other essential activities. The mounting animal itself may be experiencing discomfort from the hormonal condition driving the behavior, as pathological states like ovarian cysts can cause abdominal pain alongside behavioral changes. Group cohesion deteriorates when one member's hormonally driven behavior continually overrides normal social boundaries, potentially leading to fighting, separation anxiety, or the need to permanently separate previously bonded animals.

Testosterone is the primary hormonal driver of mounting behavior in male guinea pigs and exerts its effects through both organizational and activational mechanisms. During prenatal and early postnatal development, testosterone exposure organizes neural circuits in the hypothalamus and limbic system that will later control reproductive and aggressive behaviors. At puberty, rising testosterone levels activate these circuits, producing the full repertoire of male sexual behavior including mounting. Guinea pig males reach sexual maturity between three and five weeks of age, remarkably early compared to many other rodent species, and testosterone-driven mounting behavior can appear at this young age. Circulating testosterone levels in intact adult males are maintained by continuous production from the Leydig cells in the testes under the influence of luteinizing hormone from the anterior pituitary gland. The sustained nature of testosterone production in intact males, unlike the cyclical estrogen fluctuations in females, means that male hormonal mounting can be a constant rather than periodic phenomenon.

Estrogen and progesterone dynamics during the female guinea pig estrous cycle produce predictable behavioral changes including mounting activity. The estrous cycle of approximately 15 to 17 days involves follicular development under follicle-stimulating hormone influence, rising estrogen levels as follicles mature, a peak of estrogen that triggers the luteinizing hormone surge and ovulation, and subsequent progesterone dominance during the luteal phase. Mounting behavior in normal cycling females concentrates during the periovulatory period when estrogen levels peak and progesterone has not yet risen sufficiently to suppress behavioral estrus. During this window, females may mount other females in the group, a behavior that is entirely normal and not indicative of pathology. The brief, cyclical, and self-limiting nature of estrous-related mounting in healthy females distinguishes it from the persistent mounting seen with pathological conditions.

Ovarian cysts represent the most clinically significant pathological cause of hormonal mounting in female guinea pigs. Cystic ovarian disease is extremely common in guinea pigs, with some studies documenting prevalence rates exceeding 75 percent in females over two years of age. These cysts can be serous, producing estrogen-containing follicular fluid that elevates circulating estrogen levels chronically rather than cyclically. Sustained estrogen elevation drives persistent behavioral estrus, producing continuous mounting behavior, aggression, and restlessness that does not follow the normal cyclical pattern. The behavioral changes from ovarian cysts are often accompanied by bilateral symmetrical hair loss along the flanks, a hallmark sign resulting from estrogen's effect on hair follicle cycling. The progressive worsening of mounting behavior in a female guinea pig beyond two years of age should prompt evaluation for ovarian cysts as the driving pathology.

Adrenal gland pathology is a less common but important endocrine cause of mounting behavior in guinea pigs. The adrenal glands produce small quantities of sex steroids under normal conditions, but adrenal tumors or hyperplasia can increase production of androgens and estrogens to levels sufficient to drive mounting behavior even in neutered animals. Adrenal-origin mounting behavior is particularly suspected when a castrated male or spayed female develops or resumes mounting activity, as the gonads have been removed and cannot be the hormonal source. Adrenal disease in guinea pigs shares some clinical features with the well-characterized adrenal disease seen in ferrets, though it is less thoroughly studied in cavies. Diagnosis requires measurement of adrenal sex steroid levels or advanced imaging to identify adrenal enlargement, and treatment may involve surgical adrenalectomy or medical management with hormone-modulating drugs.

Neuroendocrine factors beyond simple hormone levels influence the expression of mounting behavior. Individual variation in receptor density for testosterone and estrogen in brain regions controlling sexual behavior means that animals with similar circulating hormone levels may express very different behavioral intensities. Stress hormones including cortisol interact with reproductive hormone pathways, and chronic stress can either suppress or paradoxically increase mounting behavior depending on the individual and the nature of the stressor. Social learning also plays a role, as guinea pigs raised in certain social configurations may develop mounting patterns that persist even after hormonal triggers are reduced. These neuroendocrine complexities explain why some guinea pigs exhibit more pronounced mounting behavior than others despite comparable hormonal status, and why behavioral management sometimes needs to complement hormonal treatment.

Normal dominance mounting is an expected and healthy component of guinea pig social behavior that occurs during hierarchy establishment and periodic reinforcement. When guinea pigs are first introduced or when group composition changes, mounting is one of several behaviors used to negotiate social rank along with rumblestrutting, chin raising, teeth chattering, and chasing. This type of mounting is typically brief, lasting only a few seconds per attempt, and occurs in bouts over the first few days to weeks of group formation before declining as the hierarchy stabilizes. Both males and females engage in dominance mounting, and it can be directed at animals of either sex. The mounted animal may submit by standing still, moving away, or producing a low rumbling vocalization signaling acceptance of subordinate status. Dominance mounting that follows this pattern, diminishes over time, and does not cause injury is entirely normal and does not require intervention.

Reproductive mounting in intact males follows a characteristic courtship sequence that distinguishes it from dominance behavior. The male typically initiates with rumblestrutting, a behavior combining a deep purring vocalization with a swaying, side-to-side hip movement as he approaches the female. He circles the female repeatedly, often lowering his head and directing his nose toward her anogenital region to assess her estrous status through scent. If the female is receptive, she adopts a lordosis posture, flattening her back and raising her hindquarters to facilitate mounting. The male then mounts from the rear, and intromission is typically brief. If the female is not receptive, she moves away, kicks backward, or produces aggressive vocalizations, and a socially appropriate male will desist after one or two rejected attempts. This complete courtship sequence, with its predictable steps and responsiveness to female signals, characterizes normal reproductive mounting.

Pathological hormonal mounting is distinguished by several key features that owners and veterinarians can identify. Persistence is the most prominent indicator: the mounting animal continues relentlessly despite clear rejection signals from the mounted animal, resuming attempts within seconds of being displaced. Escalation occurs when the mounting intensity increases over days or weeks rather than diminishing as hierarchies stabilize. Context inappropriateness includes mounting by neutered animals that should have reduced hormonal drive, mounting that occurs with equal intensity at all times rather than cyclically, or mounting directed at objects or body regions not associated with normal reproductive behavior. Physical consequences on the mounted animal, including hair loss on the back and flanks from repeated grasping, bite wounds, skin abrasions, weight loss from feeding disruption, and chronic stress behaviors such as excessive hiding or vocalizing, signal that the mounting has crossed into pathological territory.

Associated signs accompanying pathological mounting provide important diagnostic context. In females, concurrent bilateral flank hair loss, abdominal distension, vulvar swelling or discharge, and changes in the estrous cycle pattern suggest ovarian cysts as the underlying cause. In males, increased aggression beyond mounting, excessive scent marking through dragging the perineal region across cage surfaces, urine spraying, and enlargement of the grease gland on the dorsal rump suggest testosterone-driven behavior that may be intensified by social or environmental stressors. In either sex, the development of mounting behavior in a previously calm animal warrants investigation for new hormonal pathology. Age is relevant context, as mounting that emerges in a female over three years of age with no prior history of such behavior strongly suggests acquired ovarian disease rather than a temperament issue.

Veterinary evaluation of excessive mounting behavior begins with a comprehensive history that captures behavioral details, social housing context, and medical background. The veterinarian asks about the onset and progression of the behavior, including whether it appeared suddenly or escalated gradually, its temporal pattern including any cyclical variation, which animals are targeted, and whether other behavioral changes such as aggression, vocalization changes, or appetite alterations are present. The reproductive status of the animal is confirmed, including whether it has been neutered and at what age, and whether mounting behavior predated or followed the procedure. Housing configuration, the number and sex of cage mates, cage dimensions, and any recent changes in group composition provide context for assessing whether social factors are contributing to the behavior.

Physical examination focuses on the reproductive system and endocrine-sensitive structures. In females, abdominal palpation assesses for ovarian enlargement or masses, as cystic ovaries can sometimes be detected as fluctuant structures in the caudal abdomen. The vulvar region is examined for swelling, discharge, or irritation that accompanies hyperestrogenism. Hair coat condition is evaluated, with particular attention to bilateral symmetrical alopecia along the flanks that characterizes estrogen excess. Nipple enlargement may be present in hyperestrogenic females. In males, testicular palpation confirms the presence and symmetry of the testes in intact animals and verifies complete removal in castrated males, as retained testicular tissue from incomplete castration can continue to produce testosterone. The grease gland region on the dorsal rump is examined for enlargement and excess sebaceous secretion that accompanies androgen stimulation.

Diagnostic imaging is the most valuable tool for identifying the pathological causes of hormonal mounting, particularly ovarian cysts. Abdominal ultrasonography provides real-time visualization of the ovaries and can identify cystic structures, measure their size, and assess their number and laterality. Ovarian cysts in guinea pigs range from small follicular cysts a few millimeters in diameter to massive serous cysts several centimeters across that can fill a substantial portion of the abdominal cavity. Serial ultrasonography over time tracks cyst progression and guides treatment decisions. Abdominal radiography provides complementary information about organ size and position but is less sensitive than ultrasound for cyst detection. If adrenal pathology is suspected, ultrasound examination of the adrenal glands evaluates for enlargement, nodularity, or mass lesions, though the small size of guinea pig adrenal glands makes subtle changes difficult to detect.

Laboratory diagnostics support the clinical assessment by quantifying hormonal status. Serum estradiol measurement in females evaluates for the sustained elevation associated with ovarian cysts, though interpretation requires species-specific reference ranges and awareness that a single measurement may not capture cyclical variation in normal animals. Progesterone levels help distinguish between functional cysts and corpora lutea. In males, testosterone measurement can quantify androgenic status, though the correlation between circulating testosterone levels and behavioral intensity is not always linear due to individual differences in receptor sensitivity. Serum testosterone measurement is particularly useful in castrated males with mounting behavior to determine whether residual testicular tissue or adrenal androgen production is responsible. Complete blood counts and serum biochemistry panels assess general health status and screen for concurrent conditions that might influence behavior or treatment decisions.

Environmental and behavioral management represents the first line of intervention for mounting behavior and may be sufficient for mild cases without underlying pathology. Increasing cage space reduces competitive tension and provides mounted animals with escape routes and retreat areas. Adding multiple hiding houses, food stations, and water sources distributed throughout the enclosure prevents resource guarding that intensifies social conflict. Temporary separation during peak mounting periods allows the mounted animal to rest and recover from stress while the mounting animal experiences reduced stimulation. Floor time outside the cage in a neutral space can help redirect energy. Rearranging cage furniture periodically can partially reset territorial dynamics, though this technique has limited effectiveness for hormonally driven behavior as opposed to socially motivated mounting.

Neutering is the definitive treatment for mounting behavior driven by gonadal hormones in animals without other pathology. Castration of intact males removes the primary source of testosterone and typically produces significant behavioral reduction within two to six weeks, though some residual mounting may persist at lower intensity due to organizational effects on neural circuits that occurred during development and learned behavioral patterns. The surgical procedure involves removal of both testes through scrotal or inguinal incisions under general anesthesia and is considered routine by veterinarians experienced with guinea pig surgery. Post-castration, males remain fertile for approximately three to six weeks as residual sperm clear from the reproductive tract, necessitating continued separation from females during this period. Ovariectomy or ovariohysterectomy in females removes the ovaries and eliminates cyclical estrogen production, resolving estrous-related mounting and preventing the development of ovarian cysts that would drive persistent mounting in later life.

Medical treatment of ovarian cysts offers both surgical and pharmacological approaches. Surgical removal of cystic ovaries through ovariectomy or ovariohysterectomy provides definitive resolution and is the treatment of choice when the animal is a suitable surgical candidate. Some veterinarians drain large cysts percutaneously under ultrasound guidance as a temporizing measure to relieve abdominal discomfort, though cysts typically refill within weeks to months and drainage alone does not resolve the hormonal imbalance driving behavior. Hormonal medical management using gonadotropin-releasing hormone agonists such as deslorelin acetate implants has emerged as an effective alternative for guinea pigs that are poor surgical candidates or whose owners prefer non-surgical options. Deslorelin works by downregulating the pituitary-gonadal axis after an initial stimulatory phase, reducing gonadotropin secretion and consequently lowering ovarian steroid production. The implant provides sustained hormone suppression for approximately six to eighteen months before replacement is needed.

Human chorionic gonadotropin injections represent another medical option that has been used historically for ovarian cyst management in guinea pigs. Administered as a series of intramuscular injections, human chorionic gonadotropin mimics luteinizing hormone and can induce luteinization of cystic follicles, converting estrogen-producing cysts into progesterone-producing corpora lutea and reducing the estrogenic drive behind mounting behavior. Response is variable, with some animals showing rapid improvement while others require repeated treatment courses. The effect is typically temporary, as new cysts can develop from remaining follicles after treatment. Combination approaches using initial cyst drainage followed by hormonal therapy to prevent refilling, or hormonal therapy to reduce cyst size before surgical removal, may optimize outcomes in complex cases.

Pain management and supportive care address the physical and welfare consequences of both the hormonal condition and the mounting behavior itself. Animals with large ovarian cysts may experience abdominal discomfort that contributes to behavioral disturbance, and analgesic therapy with meloxicam can improve comfort and reduce agitation. Cage mates that have sustained injuries from aggressive mounting require wound assessment and treatment to prevent infection. Nutritional support ensures adequate vitamin C intake and overall caloric provision for animals whose feeding has been disrupted by social stress. Behavioral enrichment including foraging opportunities, tunnel systems, and varied substrates provides alternative outlets for the mounting animal's energy and engagement. These supportive measures complement the primary hormonal or surgical treatment and improve welfare for all animals in the group during the treatment and recovery period.

The decision to neuter a guinea pig for mounting behavior management involves weighing the benefits of behavioral modification against the inherent surgical risks in this species. Guinea pigs present specific anesthetic challenges including a narrow oropharyngeal anatomy that makes endotracheal intubation difficult, a tendency toward hypothermia during procedures due to high surface-area-to-body-mass ratio, sensitivity to certain anesthetic agents, and the risk of gastrointestinal stasis during fasting and recovery periods. These risks are manageable by veterinarians experienced in exotic animal anesthesia and surgery but are greater than the equivalent procedures in dogs or cats. The discussion between the veterinarian and owner should include a realistic assessment of surgical risk balanced against the welfare benefits of resolving persistent hormonally driven behavior, the alternatives of medical management, and the natural history of the condition without intervention.

Castration technique in guinea pigs requires attention to species-specific anatomy. The inguinal rings in guinea pigs are open, meaning the abdominal cavity communicates directly with the scrotal sac through wide inguinal canals. This open ring anatomy creates a risk of post-operative herniation of abdominal contents into the scrotal area if the inguinal rings are not closed during the procedure. Surgeons experienced with guinea pig castration routinely close the inguinal rings or use a closed castration technique that reduces herniation risk. The testes are relatively large compared to body size and have a substantial blood supply that requires careful hemostasis. Recovery from uncomplicated castration is typically rapid, with most guinea pigs resuming normal eating within 12 to 24 hours and returning to baseline activity within a few days. Post-operative monitoring focuses on appetite maintenance, pain management, and incision site assessment.

Ovariectomy and ovariohysterectomy in female guinea pigs address both mounting behavior and the underlying ovarian pathology driving it. The surgical approach is typically through a ventral midline or flank celiotomy, with the choice influenced by surgeon preference and the size and position of any ovarian cysts. Large cysts may require careful manipulation to avoid rupture during extraction, as spillage of cyst contents can cause peritoneal irritation. The broad ligament and ovarian pedicle vasculature require secure ligation to prevent hemorrhage. If ovariohysterectomy is performed rather than ovariectomy alone, the uterine body is ligated and transected, removing the entire reproductive tract. Recovery from ovarian surgery is similar in timeline to castration but may involve slightly more post-operative discomfort due to the abdominal approach. Hormonal behavioral changes following ovariectomy typically manifest within one to four weeks as circulating estrogen levels decline.

Post-neutering behavioral expectations should be discussed clearly with owners to establish realistic timelines and outcomes. Mounting behavior driven purely by gonadal hormones generally decreases significantly within two to six weeks following neutering as circulating hormone levels fall. However, mounting may not disappear entirely, as developmental organizational effects of hormones on brain circuitry create neural pathways for mounting behavior that persist independently of current hormone levels. Additionally, learned behavioral patterns may continue as habit even after the hormonal motivation diminishes. Males that were sexually experienced before castration tend to retain more residual mounting behavior than those castrated before first mating. In most cases, the reduction in mounting intensity and frequency is sufficient to restore social harmony within the group even if occasional mounting persists. Complete cessation of all mounting behavior is an unrealistic expectation and should not be set as the benchmark for treatment success.

Hormonal mounting behavior affects not only the mounting animal and its direct target but the entire social structure of the guinea pig group. Guinea pigs form hierarchical social groups where status is maintained through a combination of subtle and overt signals including vocalizations, body postures, scent marking, and physical interactions. When one animal's hormonally driven mounting becomes excessive, it disrupts the established social order by creating a constant source of tension and conflict. Subordinate animals that are persistently mounted may develop chronic stress responses including elevated cortisol levels, immunosuppression, reduced appetite, weight loss, and withdrawal from normal social participation. Even animals not directly targeted by mounting may be affected by the increased ambient tension within the group, showing stress behaviors such as increased startle responses, reduced exploration, and altered vocalization patterns.

The relationship between mounting behavior and aggression requires careful evaluation because the two are related but distinct phenomena in guinea pig social behavior. Mounting in itself is not inherently aggressive and in many contexts represents normal social communication. However, hormonally intensified mounting is frequently accompanied by escalating aggression when the mounted animal resists, leading to biting, fur pulling, and chasing that can cause significant physical injury. The progression from mounting to outright aggression often develops gradually, with the intensity of interactions increasing over days to weeks as the hormonal drive strengthens and the mounted animal's tolerance decreases. Early recognition of this escalating pattern allows intervention before serious injuries occur. If mounting consistently triggers aggressive encounters that draw blood or cause significant hair loss, temporary separation becomes necessary for the safety of all animals involved.

Management of group dynamics during treatment of hormonal mounting requires thoughtful planning to preserve social bonds while ensuring safety. Permanent separation should be considered a last resort because guinea pigs are social animals that suffer from isolation, and separated animals may develop depression, excessive vocalization, and stress-related health problems. Grid dividers within a shared cage allow visual and olfactory contact while preventing physical interactions during the most intense phase of treatment. This arrangement maintains social awareness and facilitates reintroduction once hormonal levels normalize following neutering or medical treatment. Gradual reintroduction after treatment follows a protocol of neutral-territory meetings under close supervision, progressing to shared cage time with monitoring, and finally full-time cohabitation once mounting behavior has diminished to acceptable levels.

Long-term social outcomes following successful treatment of hormonal mounting are generally favorable. Most guinea pig groups that experienced disruption from one member's excessive mounting can be successfully reunited after the hormonal condition is addressed, provided that permanent pair-bond damage has not occurred. Young animals and those in well-established groups tend to reintegrate most smoothly. Groups where mounting progressed to severe aggression with significant injuries may have sustained relationship damage that makes successful reunion difficult. In these cases, introduction protocols similar to those used for unfamiliar animals may be needed, treating the previously bonded animals as if they are meeting for the first time. The success of reintegration depends on the individual temperaments involved, the severity and duration of the mounting problem before treatment, and the completeness of hormonal resolution achieved through the chosen intervention.

Preventive strategies for hormonal mounting behavior begin with informed decisions about the reproductive status of guinea pigs at the time of acquisition. Prospective owners who plan to house guinea pigs in same-sex groups should consider early neutering to prevent testosterone-driven mounting from disrupting group harmony. Males intended for same-sex housing benefit from castration before or shortly after sexual maturity, ideally between four and six months of age when the animal is large enough for safe anesthesia but before entrenched hormonal behavior patterns develop. Early castration reduces the organizational effects of testosterone on mounting behavior circuits compared to later castration, though it is beneficial at any age. For female guinea pigs, the decision to spay is influenced by the high prevalence of ovarian cysts later in life, and some veterinarians and owners opt for prophylactic ovariectomy in young females to prevent both future cystic disease and the mounting behavior it causes.

Housing design and group composition planning help minimize the behavioral impact of normal hormonal fluctuations in intact animals. Same-sex groups should be formed with compatible individuals of similar age and temperament, introduced gradually in neutral territory with careful monitoring. Adequate cage space is critical, with minimum recommendations of at least 0.7 square meters for two guinea pigs and proportionally more for each additional animal. Cage layouts should include multiple hiding spaces, elevated platforms, and distributed resources so that subordinate animals can retreat from unwanted mounting attempts without being cornered. Enrichment that provides physical and mental stimulation, including foraging opportunities, tunnels, and varied textures, may reduce the expression of hormonally motivated behaviors by redirecting activity toward exploration and play.

Regular health monitoring facilitates early detection of hormonal conditions that drive pathological mounting. For female guinea pigs over two years of age, annual or semi-annual abdominal palpation and periodic ultrasound screening for ovarian cysts enables detection of cystic disease before behavioral consequences become severe. Weight monitoring identifies unexplained changes that may accompany hormonal disturbance. Coat condition assessment catches the bilateral flank alopecia characteristic of hyperestrogenism in its early stages. Behavioral baseline documentation, where owners note normal activity patterns, social interactions, and temperament, creates a reference against which subtle hormonal behavioral changes can be identified. Owners who maintain awareness of their guinea pig's normal behavior are best positioned to detect the early escalation of mounting that signals emerging hormonal pathology.

Owner education about the hormonal basis of mounting behavior prevents both unnecessary alarm and inappropriate neglect. Understanding that some degree of mounting is normal guinea pig behavior prevents owners from seeking unnecessary medical intervention for healthy social dynamics. Equally important, awareness that persistent or escalating mounting can signal treatable conditions such as ovarian cysts prevents owners from dismissing pathological behavior as simply a personality trait. Knowledge of the clinical signs that distinguish normal from abnormal mounting, including the associated signs of hormonal disease, empowers owners to seek veterinary evaluation at the appropriate time. Educational resources from veterinary organizations, reputable guinea pig welfare societies, and comprehensive reference libraries provide ongoing support for owners navigating the behavioral complexities of guinea pig group management.

The long-term welfare perspective on hormonal mounting behavior emphasizes that this is a manageable condition with excellent outcomes when appropriately addressed. Whether through environmental management alone for mild cases, neutering for gonadal hormone-driven behavior, or medical treatment for conditions like ovarian cysts, effective interventions exist for every severity level. The key to optimal outcomes is timely recognition that mounting has exceeded normal limits, prompt veterinary evaluation to identify any underlying pathology, and commitment to the recommended treatment plan including follow-up monitoring. Guinea pigs that receive appropriate management for hormonal mounting behavior can enjoy full, comfortable lives in stable social groups, and their cage mates benefit equally from the restoration of balanced group dynamics.