Introduction

Dogs are believed to be the first species domesticated by humans. Initially, they survived by scavenging leftover food from humans or hunting in cooperation with them (Coren, 1994; Galac and Knol, 1997). Over time, dogs transitioned from being regarded merely as property to being embraced as family members, commonly living alongside humans as companion animals.

As the human-dog living environment has evolved, behavioral issues such as aggression, separation anxiety, fear of strangers, excessive barking, and stress-induced pacing have emerged as significant challenges that must be addressed to ensure harmonious coexistence (Houpt, 1997; Landsberg et al., 1997). Barking has been interpreted as a form of communication between humans and dogs (Feddersen-Petersen, 2000), an expression of attachment to the owner (Yin, 2002), a means of interpreting the owner’s actions or instructions (Miklósi et al., 2000), or a response to vocal cues (Pongrácz et al., 2001).

However, many problematic behaviors in companion dogs are considered manifestations of stress. Notably, dogs experience considerable stress when left alone following their owner’s departure (Morris, 1986). Such stress may lead to undesirable behaviors, including destructive activities, inappropriate urination, excessive barking, and disturbances to neighbors (Marder and Voith, 1991).

With the recent increase in companion dog ownership, the incidence of behavioral problems has also been on the rise. Although previous studies have reported that the frequency of such problem behaviors may vary depending on neutering status (Houpt, 1997), research on the behavioral patterns and lifestyles of companion dogs during owner absence remains limited (Jung and Hwangbo, 2025).

Therefore, this study aims to investigate sex-based behavioral differences in companion dogs during periods of owner absence. Ultimately, the goal is to contribute to the prevention or mitigation of abnormal behaviors, thereby providing foundational data for enhancing animal welfare.

Materials and Methods

Subjects and experimental design

The subjects used in this study were Maltese dogs that were accustomed to indoor living. The experimental design was modeled after the living conditions of companion dogs in typical households. Dogs were grouped according to sex: two male dogs (aged 2 and 4 years) and two female dogs (aged 2 and 6 years), for a total of four animals. To reflect a natural home environment, the sample size was intentionally limited to minimize inter-dog influence.

Behavioral observations were conducted in the dogs’ usual home environment. A preliminary observation was carried out over four days to allow the dogs to acclimate to the CCTV equipment (EGPIS, HVR-960H04S 4-channel full WD1). The main trial was conducted for three consecutive days to allow for statistical analysis. Dogs were recorded for 8 hours per day, from 9:00 AM to 5:00 PM, immediately following the owner’s departure. Behavioral data were analyzed by frequency and duration on an hourly basis.

Observational items

The primary behavioral parameters observed in this study included sleeping, resting (break), pacing, destructiveness, barking, and looking out the window. These behaviors were selected based on prior studies by Beerda et al. (1997; 1999), which analyzed behavioral responses as indicators of stress in dogs.

Sleeping was defined as lying flat on the floor for at least five minutes with no movement. If the dog was lying down but frequently raised its head, kept its eyes open, or turned over often, it was classified as resting time. Pacing was recorded as any activity outside of sleeping, resting, and destructiveness. Destructiveness was defined as any behavior lasting longer than five seconds, including scratching walls, scratching cushions, scratching the floor, biting its own tail, knocking over food or water bowls, and damaging barriers. The time spent performing these behaviors was measured. Although destructive behavior can be interpreted as a pathological symptom caused by separation anxiety (Barbara, 2008), this study considered these behaviors as habits formed prior to socialization with the owner, likely due to time spent at animal shelters or pet shops (Serpell and Jagoe, 1995). Barking was categorized into simple barking, repetitive barking, and howling. Simple barking was recorded separately if there was a gap of five seconds or more between barks. Repetitive barking was counted as a single event if the interval between barks was less than five seconds. Howling lasted for an average of seven seconds, occasionally extending to fifteen seconds. Lookout behavior was measured by the number of times the dog directed its gaze toward a window or door.

Water and food were provided at 8:00 AM and 6:00 PM, respectively, but no observations were made on feeding behavior during the trial.

Statistical analysis

The results of this study were analyzed using the SAS (2013). Analysis of variance (ANOVA) was performed, and mean comparisons between treatments were made using t-tests and the least significant difference (LSD) test at a 5% significance level (p < 0.05).

Results and Discussion

Differences in behavioral patterns of dogs based on sex after owner’s departure

The effects of dog sex on behavioral patterns after the owner’s departure are shown in Table 1.

Among the behaviors observed, sleep duration was significantly longer in females (36.1 min) compared to males (12.2 min) (p < 0.05). Females spent approximately 60% of their time sleeping, indicating a tendency to devote a significant portion of time to sleep during the owner’s absence. Resting and pacing times were significantly longer in males, at 20 and 26 minutes respectively, compared to females (p < 0.05).

Destructive behaviors, which can result in issues such as indoor messes or property damage and in severe cases, lead to injury to the dog’s teeth, claws, or even psychological disorders have been reported (Serpell and Jagoe, 1996; Lund and Jorgensen, 1999). In this study, the time spent on destructive behaviors was the shortest among all observed behaviors, and no significant difference was found between males (1.9 min) and females (2.5 min).

Barking and lookout behavior (i.e., gazing out the window) were significantly more frequent in males, with an average of 12.6 barks and 7.2 looks compared to females (4.5 barks and 3.8 looks) (p < 0.05). Previous studies have shown that intact males exhibit a higher frequency of problem behaviors than neutered males, a trend attributed to the influence of sex hormones (Houpt, 1997). In this study, males barked approximately three times more than females during the owner’s absence, which is consistent with previous findings.

Changes in dogs’ lifestyle patterns by time of day based on sex

Table 2 shows the changes in sleep, rest, pacing, and destructive behaviors based on sex and the time of day after the owner’s departure.

Sleep time was significantly longer for females, with an average of 44 minutes between 10:00 AM and 2:00 PM, compared to males, who averaged 23 minutes during the same time frame (p < 0.05). Regarding destructive behaviors, males exhibited consistent levels of destructiveness, ranging from 1.2 to 3.2 minutes per hour, regardless of the time of day. In contrast, females displayed more concentrated destructive behavior immediately after the owner’s departure and just before sleep periods.

Destructive behavior is defined as an expression of anger and distress experienced by the dog when separated from its owner (Simpson, 2000). In the United States, approximately 17% of dogs visiting veterinary clinics exhibited symptoms of separation anxiety (Barbara, 2008), and 20 - 40% of these cases were diagnosed with severe separation anxiety (Wright and Nesselrote, 1987). This type of anxiety can lead to serious challenges in the human-animal relationship (Houpt and Reisner, 1996). Although no significant difference was observed in the overall time spent on destructive behaviors between males and females (Table 2), the temporal patterns of destructiveness differed between the sexes depending on the time of day.

Changes in unusual behaviors of dogs based on sex and time of day

The results of barking and window-looking behaviors by time of day and sex after the owner’s departure are shown in Table 3.

Barking was most frequent immediately after the owner’s departure, between 9:00 AM and 10:00 AM, with males barking an average of 20.7 times and females barking an average of 10 times (p < 0.05). The least frequent barking occurred between 12:00 PM and 1:00 PM for males, and between 10:00 AM and 12:00 PM for females (p < 0.05), but both sexes showed an increase in barking frequency thereafter.

For window-looking behavior, males showed the highest frequency, averaging 10.7 times between 9:00 AM and 10:00 AM (p < 0.05), while females showed the highest frequency between 4:00 PM and 5:00 PM, averaging 9.3 times (p < 0.05). The lowest frequency of window-looking behavior occurred between 12:00 PM and 1:00 PM for males (5.2 times on average), and between 10:00 AM and 11:00 AM for females (only 0.3 times on average) (p < 0.05).

Both sexes exhibited the highest frequency of barking and window-looking between 9:00 AM and 10:00 AM (p < 0.05), which is likely due to stress caused by separation anxiety immediately after recognizing their owner’s absence. Furthermore, the increase in barking and window-watching behaviors after 3:00 PM suggests that companion dogs may recognize the owner’s expected return time (Sheldrake, 1999). Similar behaviors have also been reported by dog owners in Germany and the United States, indicating comparable patterns in their own dogs (Sheldrake and Smart, 1997; Brown and Sheldrake, 1998).

Conclusion

This study was conducted to investigate the behavioral patterns of companion dogs based on sex in response to owner absence. The goal was to prevent or reduce problem behaviors that may lead to accidents after the owner’s departure and to provide foundational data on the behavioral tendencies of companion animals.

Observations revealed that female dogs spent significantly more time sleeping (mean 36.1 min) than males (p < 0.05), while male dogs showed significantly longer durations of resting and pacing compared to females (p < 0.05). Barking, identified as a problem behavior during owner absence, occurred significantly more frequently in males (mean 12.6 times) than in females (p < 0.05). Although there was no significant difference in the total hourly duration of destructive behavior by sex, differences were observed in temporal patterns. Males consistently exhibited destructive behavior throughout the observation period (1.2 - 3.2 min·h^-1), whereas females displayed it primarily immediately after the owner’s departure and around sleep periods. In both sexes, barking was most frequent immediately after the owner left.

Taken together, these results indicate that females slept more than three times longer than males during owner absence, while males exhibited significantly more frequent barking behavior (12.6 vs. 4.5 times). Additionally, barking frequency peaked in both sexes immediately following the owner’s departure. This study confirmed that behavioral responses to owner absence differ by sex and vary by time of day. These findings provide a basis for improving the living environment of dogs left alone and for developing sex-specific care and management programs tailored to the behavioral tendencies of companion dogs, ultimately promoting their welfare and quality of life.