1. Introduction
In times when humans are exerting increasing influence on natural ecosystems, the protection of biodiversity requires a thorough understanding of the habitat requirements of wild animals. Worldwide, landscapes are increasingly the result of intensive interaction between natural processes and human land use [
1]. Factors such as climate change, ongoing urbanization, and industrial agriculture have profoundly altered the structure of biotopes [
2,
3]. These dynamic changes present a scientific challenge in developing reliable methods of assessing habitat quality. Modeling habitat suitability for wildlife is an essential component of modern nature conservation and landscape management strategies. In particular, large mammals such as red deer (
Cervus elaphus) require careful habitat identification and analysis to consider both their ecological needs and the often-competing interests of forestry, agriculture, and hunting [
4,
5]. The increasing fragmentation of natural habitats due to human activities is one of the major challenges for maintaining healthy red deer populations as it significantly influences the animals’ movement patterns, behavior, and habitat selection [
6,
7]. Several studies have shown links between structural and ecological interactions and ecosystem quality for plants and animals at different spatial and temporal scales [
8]. However, although these interactions are understood, the available data for assessing a site’s species are often inadequate [
8]. One reason for this limitation is often restricted access to the site-specific in situ data required for assessing habitat quality, along with the availability of species-specific data. To address the lack of such data, suggested assessing individual population status by integrating various types of information. While some studies show that dominant species can control vegetation development, it is likely that dominant herbivores and carnivores in Central Europe exert similar influence on their habitats. Landscape structure can thus be viewed as an indicator of both natural and anthropogenic patterns and processes at the landscape level [
9,
10]. Extracting information to support decisions and actions for sustainable resource protection—where sustainable land use is integrated with economic considerations—requires clear and comprehensible information for evaluating the respective land use. This operationalization can be achieved by calculating landscape structure indicators or landscape metrics, which serve as indicators for detecting environmental changes [
11,
12].
A monitoring system for estimating biodiversity and habitat quality requires area-wide, up-to-date data; representative quantitative indicators; a data processing chain, models for deriving indicators; and an evaluation system. Combining different data sources is essential for identifying optimal sampling strategies. To adequately represent the complexity of dynamic systems, various monitoring strategies must be integrated for data collection [
13].
Traditional approaches to habitat modeling are often based on field data collected through telemetry studies, direct observations, or extensive fieldwork. These methods provide valuable insights but are mostly limited to small geographic areas and involve significant financial and logistical hurdles [
14,
15]. To address this challenge, the use of in situ data, such as hunting bag statistics, has recently emerged as a cost-effective alternative. Hunting data, which provide information on population distribution and density, are increasingly used as an indicator of habitat preferences, especially in combination with remote sensing data to enable large-scale modeling [
16,
17].
However, one of the major research gaps is the question of how reliable in situ data such as hunting bag statistics actually are in reflecting habitat preferences, especially when combined with medium-resolution remote sensing data. Studies show that although these data provide useful information at the landscape level, they are often not detailed enough to accurately reflect local habitat preferences [
18,
19]. Despite the increasing availability of remote sensing data, the integration of these data into wildlife habitat modeling has not yet been sufficiently researched, especially in highly fragmented and heterogeneous landscapes, as is relevant for red deer [
20]. Therefore, we test the data via a streamlined modeling approach.
Another key challenge in modeling habitat suitability for red deer is the consideration of different spatial scales. The habitat selection of red deer is influenced by both large-scale landscape structures and microhabitats. Studies have shown that fragmentation, forest edge density, and the mixing of forest and open land are crucial factors for the habitat use and movement behavior of red deer [
21,
22]. These dynamic interactions between landscape structure and habitat use are particularly relevant in areas with high human activity, where red deer are often forced to use less optimal habitats [
23]. In most parts of Germany, red deer are restricted to designated core areas. Additionally, red deer primarily retreat to the forest due to hunting pressure, despite being essentially an open-land animal. These factors should be considered in the model evaluation process.
Another important aspect that has been insufficiently studied so far is the seasonal variability of habitat use. Red deer often follow the so-called “green wave”, a seasonal migration that aims to always have access to the most nutrient-rich food sources [
4]. This aspect has often been neglected in habitat modeling, although considering seasonal changes is essential for a complete understanding of habitat selection [
24].
Therefore, the objectives of this study are as follows: (a) to predict potential habitats for red deer (Cervus elaphus) in eastern Mecklenburg-Western Pomerania based on landscape structure; (b) to mitigate the issue of insufficient habitat (in situ) data by converting hunting bag statistics into a proxy for habitat suitability; (c) to develop a streamlined habitat model by integrating various data sources, including remote sensing data, hunting bag statistics, deer-related landscape structure analysis, and statistical modeling; (d) to identify structural landscape properties that influence deer habitat quality and demonstrate how remote sensing and in situ proxy data can be integrated to explore relationships between habitat quality and landscape structure; and (e) to produce habitat suitability maps for land use planning and landscape management.
3. Results
3.1. Selection of Different Input Metrics and Reporting of Intermediate Results
The results for four all four variants (1–4) are presented, showing for each of the independent input metrics-associated regression coefficient (B) the Wald chi2 statistics of the regression coefficients and their associated p-values. For all four models, the p-values of the regression coefficients are <0.05 = 5%, indicating statistical significance at the 5% level of error, and the overall classification success is expressed by the overall classification rate for each model.
3.2. Model Variant 1
Model variant 1 (
Table 2) shows an overall classification rate of 63.7%; the Nagelkerke R
2 statistics is rather low, with a value of 0.101. The value of the Hosmer–Lemeshow statistics has a value of 96.950. The binary classification was better at predicting the “less preferred” habitats than the “preferred habitats” (68.1% versus 58.8%).
All regression coefficients of model variant 1 have a negative sign, which results in Exp(B) values < 1.0, thus indicating an inverse trend between increasing metric values and the probability of predicting preferred habitat suitability. The structural characteristics of the landscape expressed by CONTAG (aggregation of patches), MESH (relative patch structure), and GYRATE_AM (continuity of patches) have a significant influence on red deer habitat suitability.
3.3. Model Variant 2
Model variant 2 (
Table 3) shows an overall classification rate of 68.4%, the Nagelkerke R
2 statistics shows a value of 0.183, and the Hosmer–Lemeshow goodness-of-fit reaches a value of 190.577. The binary classification was better at predicting the “less preferred” habitats than the “preferred habitats” (79.4% versus 58%).
The overall classification success and both goodness-of-fit statistics are better than for variant 1. The regression coefficients for SHAPE_MN with a value of 0.797 and for PLAND with a value of 0.033 are positive, thus indicating a parallel trend between the structural characteristics expressed by these metrics and the prediction of habitat suitability. The regression coefficient for ED is negative, with a value of −0.084, thus indicating an opposite trend between prediction of habitat suitability and edge density.
3.4. Model Variant 3
Model variant 3 (
Table 4) achieves an overall classification rate of 71.4%, the Nagelkerke R
2 statistics shows a value of 0.241, and the Hosmer–Lemeshow goodness-of-fit reaches a value of 88.352. Both “less preferred” and “preferred habitats” are predicted with slightly different success rates (74.3% vs. 68.6%).
The overall classification success is better than for variants 1 and 2, indicating that the inclusion of more-detailed structural information obviously leads to a better prediction result. All six metrics contribute substantially to the classification success, although the regression coefficients for PLAND (−0.224), CONTAG (−0.043), and the MESH (−0.004) are negative, thus indicating an opposite trend between changed metric values and the predicted habitat suitability. The results of this model variant seems reasonable, as it considers structural properties at the landscape level (i.e., on a larger ecological scale) and the class level (i.e., on a smaller ecological scale) to be important.
3.5. Deriving the Final Suitability Model
To select the predictor variables for variant 4, we used the three most influential inputs from model variant 3 (
Table 4). The actual effect of a factor cannot be deduced from statistical significance alone. Therefore, the aim was to give equal consideration to statistical significance, relative effect, and transparent interpretation when selecting the input metrics for the logistic regression model. Model variant 3 showed that the combination of metrics on class and landscape level gives the best classification result. However, the interpretation of the six different, partly opposite effects is not entirely clear. To simplify the model and thus facilitate an easier interpretation, the regression coefficients of model variant 3 were standardized according to the method proposed by
Table 5 below.
The inputs with the largest relative effect are the landscape-level metrics CONTAG and MESH and the class level metrics ED and PLAND. The CONTAG index has the largest relative effect, with a value of −0.266, followed by ED for the forest class, with a value of −0.156. MESH and PLAND have the same value of 0.143, both containing information on the share of forest area. For ease of understanding, PLAND is preferred to MESH as the input for a model with three input metrics on either the class or landscape level (variant 4).
3.6. Model Variant 4
The overall classification success of model variant 4 reaches 68.8%, which is slightly lower than the success of model variant 3, but importantly, here, only three input variables were used compared to the previous six. The Nagelkerke R2 statistics shows a value of 0.199; the Hosmer–Lemeshow goodness-of-fit statistics reaches a value of 70.525. The rate of “preferred habitats” (67%) is close to the rate of 68.6% in model variant 3. This leads to the conclusion that preferred habitats can be predicted with almost the same accuracy but with fewer input variables.
Table 6 provides a comparison of the unstandardized and standardized regression coefficients. It shows that the rank or importance of the variables changes but not their overall effect. The CONTAG index increases from −0.027 to −0.166. Here, it has the greatest relative importance but works in the opposite direction. It measures the extent to which land cover types are aggregated or clumped. LAND is the least significant, with a value of 0.026 for the unstandardized coefficient, but the second most important, with a value of 0.164 for the standardized coefficient for the overall classification. In contrast, the ED index decreases in its relative importance from −0.092 to −0.065.
The predicted values were used and exported to a GIS (
Figure 4), where the distribution of “preferred” habitats is highlighted in light green, the “less preferred” habitats are color-coded in yellow, and both are shown together with the forest cover map.
4. Discussion
The results of the study on habitat modeling for red deer in Mecklenburg-Western Pomerania provide valuable insights acquired by combining remote sensing data, landscape metrics, and spatial and temporal inexact in situ data—in this case, hunting bag statistics. This study represents an important approach to enabling predictive modeling despite limited in situ data.
4.1. Discussion on the Importance of Proxy Data for Habitat Use Modeling
The integration of hunting data as proxy for habitat suitability has proven to be an effective method of predicting the potential habitat preferences of red deer in the absence of direct observation data. This is supported by the study by Chassagneux et al. [
16], which shows that hunting pressure and anthropogenic disturbance significantly influence the movement behavior of red deer. This study showed that habitat suitability is lower in areas with high hunting pressure, indicating that proxy data can function as a valid and cost-effective alternative to expensive telemetry studies.
Another example is the work of Alves et al. [
39], which uses methods such as scat and track counting to determine the habitat use of red deer. They confirm that indirect methods can provide valuable information on habitat preferences, especially in areas that are difficult to access.
4.2. Discussion on the Role of Remote Sensing
A key finding of this study is that remote sensing data provide an effective basis for modeling large-scale mammalian habitats [
18]. Despite the relatively coarse resolution of the Landsat 7 ETM+ data (30 m), significant landscape patterns in the habitat use of red deer could be identified. This highlights that remote sensing, even at medium resolution, in combination with appropriate landscape metrics, can provide valuable information for understanding animal behavior and habitat selection. For example, in a study by Oeser et al. [
49], the habitat dynamics of red deer and roe deer in Central Western Europe were investigated using similar remote sensing techniques, with Landsat data being used to analyze forest disturbance. The approach of combining low-resolution remote sensing data with hunting or telemetry data is considered a valuable approach by several authors, especially in regions with limited direct observation data. Furthermore, the study by Kwong et al. [
19] shows that remote sensing data combined with landscape metrics can provide a robust basis for habitat modeling.
4.3. Discussion on Model Performance
Four different model variants were tested in the study, which differ in their combination of different metrics. Interestingly, model variant 3, which combined metrics at both the landscape and class level, showed the highest prediction accuracy (71.4%). This shows the importance of considering habitat structures at both the local and regional levels to fully understand red deer behavior. In contrast, the simplified model variant 4, with only three of the most influential metrics, achieved a prediction accuracy of 68.8%. This shows that it is possible to reduce the number of variables without significantly losing model accuracy. This reduction has the advantage that the model is easier to interpret and the most important factors determining habitat selection can more easily be identified. Particularly noteworthy is the importance of the contact index (CONTAG), which was identified as one of the most important predictors in both models. Its negative influence underlines the red deer’s preference for heterogeneous landscapes.
4.4. Discussion on Landscape Structures
The modeling was based on various landscape metrics, which were calculated at both the class level (e.g., forest cover, edge density) and the landscape level (e.g., contagion index (CONTAG), gyration radius (GYRATE_AM)). The importance of these metrics reflects the structural preferences of the red deer.
The contact index, which measures the aggregation of landscape elements, has a negative influence on habitat preference. This could indicate that red deer prefer heterogeneous landscapes with a mixture of forest and open land areas over heavily aggregated forest areas. Edge density, a measure of the length of forest edges, also had a significant influence on habitat use. Red deer frequently use forest edges as a transition between cover and grazing, which explains the high relevance of this measure for habitat modeling. Landscape structure—in particular, the fragmentation of forest areas and the spatial arrangement of forest and open land—plays a central role in the habitat use of red deer. Studies show that red deer have complex interactions with their environment, with landscape structure having a significant influence on their movement patterns, resource use, and choice of retreat areas.
The results of this study clearly show that the index describing the connectivity of forest areas (CONTAG), the index describing fragmentation (MESH), and edge density (ED) are significant predictors of red deer habitat suitability. These metrics are consistent with the results of Walter et al. [
7], which show that the size of the home range of red deer is highly dependent on landscape composition and configuration. In more fragmented landscapes, the freedom of movement of red deer is restricted, which, in turn, leads to lower habitat suitability. Bevanda et al. [
6] emphasize that fragmentation of forest areas significantly increases the size of red deer home ranges as they are forced to travel greater distances to find sufficient food and cover. In more fragmented landscapes, red deer are less able to find their preferred habitats, which can affect their fitness and survival.
Sigrist et al. [
22] point out that fragmentation not only reduces food availability but also the ability to seek shelter from predators and human disturbance. In fragmented landscapes with high edge lengths, red deer are more exposed, which means that they have to adapt their behavior more often by moving to less suitable areas.
Studies such as those by Oeser et al. [
49] and Walter et al. [
7] show that red deer are able to use resources efficiently in well-connected landscapes, while also having smaller, better-defined home ranges. Connectivity allows red deer to move freely between feeding and shelter areas, increasing their fitness and survival, especially during challenging seasons such as winter. Furthermore, Wu et al. [
50] and Sun et al. [
51] show that factors such as proximity to water sources, the degree of cover provided by shrubs, and distance to roads and villages are crucial for the habitat preferences of red deer.
The present results also show that human activities, especially habitat fragmentation by agriculture and infrastructure, have a significant impact on habitat use. The negative effects of fragmentation on habitat suitability observed in this study are consistent with the results of Dechen Quinn et al. [
52], who found that white-tailed deer have smaller home ranges in more fragmented landscapes. This highlights the importance of maintaining contiguous forest patches for the long-term survival of red deer populations. Walter et al. [
7] also emphasize that deer require larger home ranges in more fragmented areas to access the resources they need. These findings are particularly relevant for landscape management in Mecklenburg-Vorpommern, where fragmentation caused by human activities is widespread.
4.5. Discussion on Seasonal Dynamics and Phenology
A very important result of this study is its calculation of seasonal habitat use dynamics. As Mysterud et al. [
4] and Sigrist et al. [
22] show, red deer follow the “green wave” to maximize access to nutrient-rich food during the growing season. This is particularly relevant in fragmented areas where the availability of high-quality forage is subject to seasonal fluctuations. The present study shows that seasonal variability in vegetation is a crucial factor for habitat suitability, underlining the importance of a dynamic consideration of habitat preferences. These findings are critical for management, particularly with regard to the effects of climate change on vegetation patterns and availability.
5. Management Implications
The findings on the influence of landscape structure on red deer habitat use have important implications for wildlife management. They suggest that maintaining contiguous forest patches and reducing fragmentation are key strategies for improving habitat quality for red deer.
Bevanda et al. [
6] and Mysterud et al. [
4] emphasize that management strategies should aim to create corridors between fragments to improve connectivity and promote the movement of red deer.
To minimize the negative influence of hunting pressure on red deer populations, sustainable hunting management plans should be implemented. This includes regulating hunting seasons to take into account reproductive cycles and introducing quotas to avoid overhunting. According to Jarnemo et al. [
40], heavily hunted populations tend to retreat into remote, inaccessible areas. Better-coordinated hunting management could help prevent the displacement of red deer from high-quality habitat and keep the population at a healthy level.
A crucial factor in supporting the red deer is protecting key habitats such as dense forests, wetlands, and wooded areas at higher elevations. These areas provide the red deer with food and shelter from human disturbance. One way to protect these key habitats is to establish buffer zones around them, where human activities such as agriculture, forestry, and recreation are restricted. According to Oeser et al. [
49], such buffer zones are particularly important for minimizing the impact of disturbance while providing the red deer with the cover and security they need for reproduction and survival.
6. Conclusions
This study shows that combining remote sensing data and proxy data, such as hunting bag statistics, is an effective way to model the habitat use of red deer in areas with limited in situ data. The application of landscape metrics has shown that even data with a low resolution, such as those from Landsat 7, can provide sufficient results. The importance of landscape structure was emphasized by the analysis of metrics such as the contagion index and edge density. These indices have a significant influence on habitat suitability and confirm the red deer’s preference for heterogeneous, unfragmented landscapes. The seasonal dynamics of vegetation—in particular, the availability of food resources—play a crucial role in the habitat selection of red deer. This highlights the need to consider seasonal and phenological changes in future management strategies. The integration of hunting data as a proxy variable showed that this method is very reliable for identifying preferred and less-preferred habitats. Hunting data could therefore be a cost-effective alternative to direct telemetry studies, especially in regions that are difficult to access. These research results suggest that the preservation of unfragmented forest areas and the creation of corridors between habitat fragments are crucial for the long-term survival of red deer populations. Landscape fragmentation has been shown to have a negative impact on the animals’ freedom of movement and resource use.
Future studies should further explore the use of modern technologies such as high-resolution remote sensing data to improve habitat modeling and better capture dynamic changes in the landscape. The results of this work can be transferred to other large mammals with similar ecological requirements.